Method for Manufacturing Display Device

ABSTRACT

A light-absorbing layer is selectively formed over an insulating surface, an insulating layer is formed over the insulating surface and the light-absorbing layer, the insulating surface, the light-absorbing layer, and the insulating layer are irradiated with laser light to selectively remove only the insulating layer above the light-absorbing layer in an irradiated region of the insulating layer so that an opening reaching the light-absorbing layer is formed in the insulating layer, and a conductive film is formed in the opening so as to be in contact with the light-absorbing layer. By forming the conductive film in the opening so as to be in contact with the exposed light-absorbing layer, the conductive film can be electrically connected to the light-absorbing layer with the insulating layer interposed therebetween.

TECHNICAL FIELD

The present invention relates to a method for manufacturing a display device including a stacked-layer structure of thin films, and specifically relates to a process for forming an opening in a thin film in a process for manufacturing a display device.

BACKGROUND ART

Each of a thin film transistor (hereinafter also referred to as a “TFT”) and an electronic circuit using the thin film transistor is manufactured as follows: various thin films such as a semiconductor film, an insulating film, a conductive film, and the like are stacked over a substrate, and a predetermined pattern is formed by a photolithography technique as appropriate. The photolithography technique is a technique in which a pattern of a circuit or the like which is formed of a material which does not transmit light over a transparent flat plate, a so-called photomask, is printed on a substrate by using light. It has been widely used in a process for manufacturing a semiconductor integrated circuit or the like.

A conventional manufacturing process using the photolithography technique requires a plurality of steps including light exposure, development, baking, and peeling only for treating a mask pattern formed of a photosensitive organic resin material called a photoresist. Therefore, the manufacturing cost is inevitably increased as the frequency of the photolithography processes is increased. In order to solve such a problem, it has been attempted to manufacture a TFT with a smaller frequency of photolithography processes (Reference 1: Japanese Published Patent Application No. 2000-133636). In Reference 1, after a resist mask formed by a photolithography process is used once, it is swelled to expand its volume and used again as a resist mask having a different shape.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a technique which is capable of manufacturing TFTs, or electronic circuits or display devices including the TFTs at low cost with a high yield even over a large substrate having a side length of 1 meter or longer, in which the frequency of photolithography processes is reduced in a manufacturing process to simplify the manufacturing process.

In the present invention, in the case where thin films (each of which is a conductive layer or a semiconductor layer) which are stacked with an insulating layer interposed therebetween are electrically connected to each other, an opening (a so-called contact hole) is formed in the insulating layer. In this case, a mask layer is not formed over the insulating layer, and the opening is selectively formed by laser light irradiation. After a light-absorbing layer which absorbs irradiated light is formed and an insulating layer is stacked over the light-absorbing layer, a region at which an opening is to be formed in the stacked layer of the light-absorbing layer and the insulating layer is irradiated with laser light from the insulating layer side. Although the laser light is transmitted through the insulating layer, it is absorbed in the light-absorbing layer. The light-absorbing layer is heated by energy of the absorbed laser light and damages the insulating layer stacked thereover. Accordingly, the opening is formed in the insulating layer, so that the light-absorbing layer below the insulating layer is exposed on a bottom surface of the opening. The light-absorbing layer may evaporate depending on the irradiation energy of laser light. The light-absorbing layer (or a thin film which is stacked below the light-absorbing layer) which is exposed on the bottom surface of the opening may be removed by etching using the insulating layer having the opening as a mask after opening formation by laser light irradiation.

In the present invention, since the opening is formed in the upper insulating layer by light absorption of the light-absorbing layer, the opening is formed so as to overlap (be in contact with) the light-absorbing layer in the insulating layer, only at a region which is irradiated with laser light. A region (shape) of the opening formed in the insulating layer reflects not only a shape of a region irradiated with laser light but also a shape of the light-absorbing layer formed therebelow. That is, a region where a formation region of the light-absorbing layer overlaps the region irradiated with laser light can form an opening region; therefore, openings having various shapes can be formed by controlling the shape of the light-absorbing layer and the region irradiated with laser light (an irradiated spot). For example, even when a laser beam spot with a large diameter is used, a minute opening with a smaller diameter can be formed by forming the light-absorbing layer selectively. Further, by changing the region irradiated with laser light in the light-absorbing layer even when a beam spot having the same shape is used, a plurality of openings having different shapes can be formed. Therefore, various opening shapes can be selected, so that design freedom of a structure of a wiring or the like included in a display device or a semiconductor device is improved.

In the case where the light-absorbing layer is formed of a conductive material such as a conductive layer using a conductive material or a semiconductor layer using a semiconductor material, by forming a conductive film in the opening so as to be in contact with the exposed light-absorbing layer, the light-absorbing layer and the conductive film can be electrically connected to each other with the insulating layer interposed therebetween. That is, in the present invention, opening formation in the insulating layer which is formed over the light-absorbing layer which functions as a conductive layer or a semiconductor layer is performed by laser light irradiation to the light-absorbing layer, so that the opening is formed in the insulating layer above a laser irradiated region of the light-absorbing layer by laser ablation.

Since the opening can be selectively formed by laser light, it is not necessary to form a mask layer, so that the number of steps and materials can be reduced. Further, there are advantages in that the insulating layer can be processed into a predetermined shape with high precision since laser light can be condensed into an extremely small spot, and the region other than a processed region is not heated substantially since heating is performed for a short period of time and instantaneously.

Further, a conductive layer, a semiconductor layer, or the like used in processing a thin film into a desired pattern is selectively formed so as to have a desired shape without using a photolithography process. A light-absorbing film such as a conductive film or a semiconductor film is formed over a light-transmitting transposing substrate and is irradiated with laser light from the transposing substrate side, so that the light-absorbing film corresponding to a laser light irradiated region is transposed to a transposed substrate, thereby forming the conductive layer or the semiconductor layer which is the light-absorbing layer with a desired shape (pattern). In this specification, the substrate over which the conductive film or the semiconductor film which is the light-absorbing film is formed and is irradiated with laser light in the first step is referred to as the transposing substrate, and the substrate over which the conductive layer or the semiconductor layer which is the light-absorbing layer is selectively formed finally is referred to as the transposed substrate. Since the conductive layer or the semiconductor layer which is the light-absorbing layer can be selectively formed to have a desired shape without using a photolithography process, a manufacturing process can be simplified and cost can be reduced, for example.

According to one feature of a method for manufacturing a display device of the present invention, a light-absorbing layer is selectively formed on an insulating surface, an insulating layer is formed over the insulating surface and the light-absorbing layer, the insulating surface, the light-absorbing layer, and the insulating layer are irradiated with laser light so that only the insulating layer over the light-absorbing layer in a laser light irradiated region of the insulating layer is selectively removed to form an opening reaching the light-absorbing layer in the insulating layer, and a conductive film is formed in the opening so as to be in contact with the light-absorbing layer.

According to one feature of a method for manufacturing a display device of the present invention, a conductive layer is selectively formed on an insulating surface, a light-absorbing layer is formed over the conductive layer, an insulating layer is formed over the insulating surface and the light-absorbing layer, the insulating surface, the light-absorbing layer, and the insulating layer are irradiated with laser light so that only the insulating layer over the light-absorbing layer in a laser light irradiated region of the insulating layer is selectively removed to form an opening reaching the light-absorbing layer in the insulating layer, and a conductive film is formed in the opening so as to be in contact with the light-absorbing layer.

According to one feature of a method for manufacturing a display device of the present invention, a conductive layer is selectively formed on an insulating surface, a light-absorbing layer is formed over the conductive layer, an insulating layer is formed over the insulating surface and the light-absorbing layer, the insulating surface, the light-absorbing layer, and the insulating layer are irradiated with laser light so that the light-absorbing layer at a laser light irradiated region and only the insulating layer over the light-absorbing layer in a laser light irradiated region of the insulating layer are selectively removed to form an opening reaching the light-absorbing layer and the conductive layer in the insulating layer, and a conductive film is formed in the opening so as to be in contact with the light-absorbing layer and the conductive layer.

According to one feature of a method for manufacturing a display device of the present invention, a plurality of light-absorbing layers are formed on an insulating surface, an insulating layer is formed over the insulating surface and the plurality of light-absorbing layers, the insulating surface, the plurality of light-absorbing layers, and the insulating layer are irradiated with laser light so that only the insulating layer over the plurality of light-absorbing layers in a laser light irradiated region of the insulating layer is selectively removed to form a plurality of openings in the insulating layer, and a conductive film is formed in each of the plurality of openings so as to be in contact with each of the plurality of light-absorbing layers.

It is necessary that the light-absorbing layer formed as described above absorb irradiated laser light, and it can be a conductive layer in the case of using a conductive material and can be a semiconductor layer in the case of using a semiconductor material. The light-absorbing layer can be used as any conductive layer or semiconductor layer included in the display device. For example, as a conductive layer, it can be used for a wiring layer, a gate electrode layer, a source electrode layer, a drain electrode layer, a pixel electrode layer, or the like.

In the above-described structure, a conductive material can be used as the light-absorbing layer. For example, one or a plurality of kinds of chromium, tantalum, silver, molybdenum, nickel, titanium, cobalt, copper, and aluminum can be used. Further, indium tin oxide (ITO), indium tin oxide containing silicon oxide (ITSO), zinc oxide (ZnO), indium tin oxide containing silicon oxide, a conductive material in which zinc oxide is doped with gallium (Ga), or indium zinc oxide (IZO) may also be used.

Further, a semiconductor material may also be used as the light-absorbing layer. For example, an inorganic semiconductor material such as silicon, germanium, silicon germanium, gallium arsenide, molybdenum oxide, tin oxide, bismuth oxide, vanadium oxide, nickel oxide, gallium arsenide, gallium nitride, indium oxide, indium phosphide, indium nitride, cadmium sulfide, cadmium telluride, or strontium titanate can be used. The light-absorbing layer may also be added with hydrogen or an inert gas (e.g., helium (He), argon (Ar), krypton (Kr), neon (Ne), or xenon (Xe)). The insulating layer in which the opening is formed can be formed of a material which transmits laser light, such as a light-transmitting inorganic insulating material or an organic resin. Further, the opening may be formed in the insulating layer by using laser light having a wavelength which is transmitted through the insulating layer.

The present invention can also be applied to a display device that is a device having a display function, and the display device using the present invention includes the following: a light-emitting display device in which a light-emitting element including a layer containing an organic material, an inorganic material, or a mixture of an organic material and an inorganic material, which exhibits light emission called electroluminescence (hereinafter also referred to as EL), between electrodes is connected to a TFT; a liquid crystal display device using a liquid crystal element containing a liquid crystal material as a display element; and the like. In the present invention, a display device means a device including a display element (e.g., a liquid crystal element or a light-emitting element). Note that the display device may also mean a main body of a display panel in which a plurality of pixels including display elements such as liquid crystal elements or EL elements and a peripheral driver circuit for driving the pixels are formed over a substrate. Further, the display device may also include a flexible printed circuit (FPC) or a printed wiring board (PWB) (e.g., an IC, a resistor, a capacitor, an inductor, or a transistor). Further, the display device may also include an optical sheet such as a polarizing plate or a retardation film. Further, a backlight (including a light guide plate, a prism sheet, a diffusion sheet, a reflection sheet, a light source such as an LED or a cold-cathode tube, or the like) may also be included.

Note that the display element or the display device can employ various modes and include various elements. For example, a display medium of which contrast is changed by an electromagnetic effect can be used, such as an EL element (e.g., an organic EL element, an inorganic EL element, or an EL element containing an organic material and an inorganic material), an electron discharging element, a liquid crystal element, an electron ink, a grating light valve (GLV), a plasma display panel (PDP), a digital micromirror device (DMD), a piezoelectric ceramic display, or a carbon nanotube. Note that the display device using the EL element includes an EL display; the display device using the electron discharging element includes a field emission display (FED), a surface-conduction electron-emitter display (SED), and the like; the display device using the liquid crystal element includes a liquid crystal display, a transmissive liquid crystal display, a semi-transmissive liquid crystal display, and a reflective liquid crystal display; and the display device using the electron ink includes electronic paper.

Further, by using the present invention, a device including a circuit including a semiconductor element (e.g., a transistor, a memory element, or a diode) or a semiconductor device such as a chip including a processor circuit can be manufactured. Note that in the present invention, a semiconductor device means a device which can function by utilizing semiconductor characteristics.

By the present invention, components such as a wiring and the like included in a display device or the like and a contact hole for electrically connecting them with an insulating layer interposed therebetween can be formed with a complicated photolithography process reduced. Accordingly, a display device can be manufactured through a simplified process, so that loss of materials and the cost can be reduced. High performance and highly reliable display devices can be manufactured with a high yield.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A1 and 1A2, 1B1 and 1B2, 1C1 and 1C2, and 1D1 and 1D2 are schematic diagrams showing the present invention.

FIGS. 2A to 2D are schematic diagrams showing the present invention.

FIGS. 3A to 3C are schematic diagrams showing the present invention.

FIGS. 4A1 and 4A2, 4B1 and 4B2, 4C1 and 4C2, and 4D1 and 4D2 are schematic diagrams showing the present invention.

FIG. 5 is a diagram showing a display device of the present invention.

FIG. 6 is a diagram showing a display device of the present invention.

FIG. 7 is a diagram showing a display device of the present invention.

FIGS. 8A to 8C are diagrams showing a method for manufacturing a display device of the present invention.

FIGS. 9A to 9C are diagrams showing a method for manufacturing a display device of the present invention.

FIGS. 10A to 10C are diagrams showing a method for manufacturing a display device of the present invention.

FIGS. 11A to 11C are diagrams showing a method for manufacturing a display device of the present invention.

FIGS. 12A to 12C are diagrams showing a method for manufacturing a display device of the present invention.

FIGS. 13A and 13B are diagrams showing a method for manufacturing a display device of the present invention.

FIGS. 14A to 14C are schematic diagrams showing the present invention.

FIGS. 15A and 15B are diagrams showing a display device of the present invention.

FIG. 16 is a cross-sectional diagram showing a structure example of a display module of the present invention.

FIGS. 17A to 17C are diagrams showing a display device of the present invention.

FIG. 18 is a diagram showing a display device of the present invention.

FIGS. 19A and 19B are diagrams showing a display device of the present invention.

FIGS. 20A and 20B are cross-sectional diagrams each showing a structure example of a display module of the present invention.

FIG. 21 is a diagram showing a display device of the present invention.

FIGS. 22A to 22D are diagrams each showing a structure of a light-emitting element applicable to the present invention.

FIGS. 23A to 23C are diagrams each showing a structure of a light-emitting element applicable to the present invention.

FIGS. 24A to 24C are diagrams each showing a structure of a light-emitting element applicable to the present invention.

FIGS. 25A to 25C are top diagrams each of a display device of the present invention.

FIGS. 26A and 26B are top diagrams each of a display device of the present invention.

FIG. 27 is a block diagram showing a main structure of an electronic device to which the present invention is applied.

FIGS. 28A and 28B are diagrams each showing an electronic device to which the present invention is applied.

FIGS. 29A to 29E are diagrams each showing an electronic device to which the present invention is applied.

FIG. 30 is a diagram showing a structure of a laser direct writing system applicable to the present invention.

FIG. 31 is a diagram showing a circuit structure in the case where a scan line driver circuit includes a TFT in a display panel of the present invention.

FIG. 32 is a diagram showing a circuit structure in the case where a scan line driver circuit includes a TFT in a display panel of the present invention (a shift register circuit).

FIG. 33 is a diagram showing a circuit structure in the case where a scan line driver circuit includes a TFT in a display panel of the present invention (a buffer circuit).

BEST MODE FOR CARRYING OUT THE INVENTION

Although the present invention will be described in detail by way of embodiment modes with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the sprit and scope of the present invention, they should be construed as being included therein. Note that in structures of the present invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in common through the drawings, and repetitive description thereof is omitted.

Embodiment Mode 1

In this embodiment mode, a method for forming a contact hole in order to manufacture a display device at low cost through a highly reliable, more simplified process is described with reference to FIGS. 1A1 and 1A2, 1B1 and 1B2, 1C1 and 1C2, and 1D1 and 1D2.

In the case where thin films (each of which is a conductive layer or a semiconductor layer) which are stacked with an insulating layer interposed therebetween are electrically connected to each other, an opening (a so-called contact hole) is formed in the insulating layer. In this case, a mask layer is not formed over the insulating layer, and the opening is selectively formed by laser light irradiation. After a light-absorbing layer which absorbs irradiated light is formed and an insulating layer is stacked over the light-absorbing layer, a region at which an opening is to be formed in the stacked layer of the light-absorbing layer and the insulating layer is irradiated with laser light from the insulating layer side. Although the laser light is transmitted through the insulating layer, it is absorbed in the light-absorbing layer. The light-absorbing layer is heated by energy of the absorbed laser light and damages the insulating layer stacked thereover. Accordingly, the opening is formed in the insulating layer, so that the light-absorbing layer below the insulating layer is exposed on a bottom surface of the opening. The light-absorbing layer may evaporate depending on the irradiated energy of laser light. The light-absorbing layer (or a thin film which is stacked below the light-absorbing layer) which is exposed on the bottom surface of the opening may be removed by etching using the insulating layer having the opening as a mask after opening formation by laser light irradiation.

In this embodiment mode using the present invention, since the opening is formed in the upper insulating layer by light absorption of the light-absorbing layer, the opening is formed so as to overlap (be in contact with) the light-absorbing layer in the insulating layer, only at a region which is irradiated with laser light. A region (shape) of the opening formed in the insulating layer reflects not only a shape of a region irradiated with laser light but also a shape of the light-absorbing layer formed therebelow. That is, a region where a formation region of the light-absorbing layer overlaps the region irradiated with laser light can form an opening region; therefore, openings having various shapes can be formed by controlling the shape of the light-absorbing layer and the region irradiated with laser light (an irradiated spot).

In the case where the light-absorbing layer is formed of a conductive material such as a conductive layer using a conductive material or a semiconductor layer using a semiconductor material, by forming a conductive film in the opening so as to be in contact with the exposed light-absorbing layer, the light-absorbing layer and the conductive film can be electrically connected to each other with the insulating layer interposed therebetween. That is, in the present invention, opening formation in the insulating layer which is formed over the light-absorbing layer which functions as a conductive layer or a semiconductor layer is performed by laser light irradiation to the light-absorbing layer formed selectively, so that the opening is formed in the insulating layer above a laser irradiated region of the light-absorbing layer by laser ablation.

Since the opening can be selectively formed by laser light and the light-absorbing layer, it is not necessary to form a mask layer, so that the number of steps and materials can be reduced. Further, there are advantages in that the insulating layer can be processed into a predetermined shape with high precision since laser light can be condensed into an extremely small spot, and the region other than a processed region is not heated substantially since heating is performed for a short period of time and instantaneously.

FIGS. 1A2, 1B2, 1C2, and 1D2 are top diagrams each of a conductive layer, and FIGS. 1A1, 1B1, 1C1, and 1D1 are cross-sectional diagrams taken along line Y-Z in FIGS. 1A2, 1B2, 1C2, and 1D2, respectively.

Specific description is made with reference to FIGS. 1A1, 1A2, 1B1, 1B2, 1C1, 1C2, 1D1, and 1D2. In this embodiment mode, as shown in FIGS. 1A1, 1A2, 1B1, 1B2, 1C1, 1C2, 1D1, and 1D2, a light-absorbing layer 701 and an insulating layer 702 are formed over a substrate 700. In this embodiment mode, a conductive material is used as the light-absorbing layer 701, thereby functioning as a conductive layer. In this embodiment mode, chromium is used as the light-absorbing layer 701. As shown in FIG. 1A2, the light-absorbing layer 701 is formed selectively over the substrate 700 so as not to cover an entire surface of the substrate 700.

As shown in FIG. 1B1, the insulating layer 702, the light-absorbing layer 701, and the substrate 700 are selectively irradiated with laser light 703 from the insulating layer 702 side. As shown in FIG. 1B2, part of the light-absorbing layer 701 and part of the substrate 700 are irradiated with the laser light 703 to form an irradiated region 704. By the irradiated energy, the insulating layer 702 only above the irradiated region is selectively removed, so that an opening 705 can be formed (see FIGS. 1C1 and 1C2). In FIG. 1C1, the insulating layer 702 is separated into insulating layers 706 a and 706 b. A conductive film 707 is formed in the opening 705 at which the light-absorbing layer 701 is exposed, thereby electrically connecting to the light-absorbing layer 701 (see FIGS. 1D1 and 1D2).

In this embodiment mode, since the opening 705 is formed in the upper insulating layer 702 by light absorption of the light-absorbing layer 701, the opening 705 is formed so as to overlap (be in contact with) the light-absorbing layer 701 in the insulating layer 702, only at the laser light irradiated region 704 which is a region irradiated with the laser light 703. Therefore, the opening 705 is formed in the insulating layer 702 above a region where the light-absorbing layer 701 overlaps the laser light irradiated region 704 as shown in FIG. 1C2. A region (shape) of the opening formed in the insulating layer reflects not only a shape of the laser light irradiated region 704 but also a shape of the light-absorbing layer formed therebelow.

That is, a region where a formation region of the light-absorbing layer overlaps the laser light irradiated region can form an opening region; therefore, openings having various shapes can be formed by controlling the shape of the light-absorbing layer and the laser light irradiated region (an irradiated spot). For example, even when a laser beam spot with a large diameter is used, a minute opening with a smaller diameter can be formed by forming the light-absorbing layer selectively. Further, by changing the irradiated region in the light-absorbing layer even when a beam spot having the same shape is used, a plurality of openings having different shapes can be formed. Therefore, various opening shapes can be selected, so that design freedom of a structure of a wiring or the like included in a display device or a semiconductor device is improved.

Irradiation with laser light may be selectively performed by a direct writing method, or may be selectively performed with a mask such as a photomask, a phase shift mask, or the like. As typical examples of a mask, there are a light shielding layer, a reflective layer, a microlens, a phase shift mask, and the like.

An example in which irradiation with laser light is selectively performed using a photomask is shown in FIGS. 14A to 14C. As shown in FIG. 14A, a conductive layer 152 is formed over a substrate 150, a light-absorbing layer 151 is formed over the conductive layer 152, and an insulating layer 156 is formed over the conductive layer 152 and the light-absorbing layer 151. As shown in FIG. 14B, by a photomask in which metal films 162 a and 162 b are selectively provided over a substrate 161, laser light is partially shielded, so that the insulating layer 156, the light-absorbing layer 151, and the conductive layer 152 are selectively irradiated with laser light 160 having transmitted through the photomask. By irradiation with the laser light 160, an opening 155 is formed in the insulating layer above the light-absorbing layer 151, so that the insulating layer 156 is separated into insulating layers 157 a and 157 b. Next, a conductive film 154 is formed so as to be in contact with the light-absorbing layer 151 which is exposed at the opening 155 as shown in FIG. 14C, thereby electrically connecting to the conductive layer 152 and the light-absorbing layer 151.

A laser beam writing system for irradiating a processing region with laser light (also called a laser beam) is described with reference to FIG. 30. In this embodiment mode, a laser beam direct writing system is used because the processing region is directly irradiated with a laser beam. As shown in FIG. 30, a laser beam direct writing system 1001 includes the following: a personal computer (hereinafter referred to as a PC) 1002 for carrying out various kinds of controls upon irradiation with a laser beam; a laser oscillator 1003 for outputting a laser beam; a power source 1004 of the laser oscillator 1003; an optical system (an ND filter) 1005 for attenuating a laser beam; an acousto-optic modulator (AOM) 1006 for modulating the intensity of a laser beam; an optical system 1007 including a lens for enlarging or reducing a cross section of a laser beam, a mirror for changing a light path, and the like; a substrate transfer mechanism 1009 having an X stage and a Y stage; a D/A converter 1010 for converting control data outputted from the PC from digital data to analog data; a driver 1011 for controlling the acousto-optic modulator 1006 depending on an analog voltage outputted from the D/A converter; and a driver 1012 for outputting a driving signal for driving the substrate transfer mechanism 1009.

As the laser oscillator 1003, a laser oscillator that is capable of emitting ultraviolet light, visible light, or infrared light can be used. The following laser oscillator can be used: an excimer laser oscillator such as KrF, ArF, XeCl, or Xe; a gas laser oscillator such as He, He—Cd, Ar, He—Ne, or HF; a solid-state laser oscillator using a crystal such as YAQ GdVO₄, YVO₄, YLF, or YAlO₃ doped with Cr, Nd, Er, Ho, Ce, Co, Ti, or Tm; or a semiconductor laser oscillator such as GaN, GaAs, GaAlAs, or InGaAsP. Note that, in the case of the solid-state laser oscillator, any one of first to fifth harmonics is preferably used. In order to adjust the shape or path of laser light emitted from the laser oscillator, an optical system including a shutter, a reflector such as a mirror or a half mirror, a cylindrical lens, a convex lens, or the like may be provided.

Further, the repetition rate of laser light of pulsed oscillation may be 0.5 MHz or more, which is extremely higher than the conventional repetition rate which is the repetition rate from several tens to several hundreds Hz, for performing laser crystallization. A pulsed laser having a pulse width on the order of picoseconds, or on the order of femtoseconds (10⁻¹⁵ seconds) can also be used.

Further, the irradiation with laser light may also be performed in an inert gas atmosphere of a rare gas, nitrogen, or the like. The irradiation with laser light may also be performed under reduced pressure.

Next, treatment for modifying quality of a film with the laser beam direct writing system is described. When a substrate 1008 is put on the substrate transfer mechanism 1009, the PC 1002 detects a position of a marker that is marked on the substrate, with a camera (not shown). The PC 1002 generates transfer data for transferring the substrate transfer mechanism 1009 based on the positional data of the detected marker and data for a lithography pattern which is inputted in advance. After that, by controlling the amount of output light for the acousto-optic modulator 1006 with the driver 1011 in the PC 1002, a laser beam outputted from the laser oscillator 1003 is attenuated by the optical system 1005, and is adjusted to a predetermined amount by the acousto-optic modulator 1006. On the other hand, a laser beam outputted from the acousto-optic modulator 1006 changes its light path and beam shape in the optical system 1007. After that, the laser beam is condensed by the lens, and a base film formed over the substrate is irradiated with the condensed laser beam, so that the treatment for modifying film quality is performed. At this time, the substrate transfer mechanism 1009 is controlled to be transferred in X and Y directions in accordance with the transfer data generated by the PC 1002. As a result, a predetermined portion is irradiated with laser beam, so that treatment for modifying film quality is performed.

The shorter the wavelength of laser beam is, the shorter in diameter the laser beam can be condensed. Therefore, in order to process a region with a minute width, a short wavelength laser beam is preferably used.

Further, a spot shape of the laser beam on the film surface is processed to have a dotted, circular, elliptic, rectangular, or linear (exactly, a narrow rectangular) shape by the optical system.

Further, although FIG. 30 shows an example of the system in which a front surface of the substrate is irradiated with a laser beam to be exposed, a laser beam writing system in which a back surface of the substrate is irradiated with a laser beam to be exposed may also be used by changing the optical system and the substrate transfer system as appropriate.

Note that, although the substrate is selectively irradiated with laser beam while being transferred here, the present invention is not limited thereto. Irradiation with laser beam can be performed while scanning the laser beam in the X- and Y-axis directions. In this case, a polygon mirror or a galvanometer mirror is preferably used for the optical system 1007.

The light-absorbing layer can be formed by an evaporation method, a sputtering method, a PVD (Physical Vapor Deposition) method, a CVD (Chemical Vapor Deposition) method such as a low-pressure CVD (LPCVD) method or a plasma CVD method, or the like. Further, a method by which a component can be printed or drawn to be a desired pattern, such as various printing methods (a method for forming a component to be a desired pattern, e.g., screen (mimeograph) printing, offset (planograph) printing, relief printing, or gravure (intaglio) printing), a dispenser method, a selective-coating method, or the like can also be used.

As the light-absorbing layer, one or a plurality of kinks of chromium, molybdenum, nickel, titanium, cobalt, copper, tungsten, and aluminum can be used. Further, indium tin oxide (ITO), indium tin oxide containing silicon oxide (ITSO), zinc oxide (ZnO), indium tin oxide containing silicon oxide, a conductive material in which zinc oxide is doped with gallium (Ga), or indium zinc oxide (IZO) may also be used. Further, a semiconductor material can also be used as the light-absorbing layer. For example, an inorganic semiconductor material such as silicon, germanium, silicon germanium, arsenic gallium, molybdenum oxide, tin oxide, bismuth oxide, vanadium oxide, nickel oxide, zinc oxide, gallium arsenide, gallium nitride, indium oxide, indium phosphide, indium nitride, cadmium sulfide, cadmium telluride, or strontium titanate can be used. Further, hydrogen or an inert gas (e.g., helium (He), argon (Ar), krypton (Kr), neon (Ne), or xenon (Xe)) may also be added to the light-absorbing layer. The insulating layer in which the opening is formed can be formed of a material which transmits laser light, such as a light-transmitting inorganic insulating material, an organic resin, or the like.

FIGS. 1A1, 1A2, 1B1, 1B2, 1C1, 1C2, 1D1, and 1D2 show an example in which the opening 705 is formed in the insulating layer 702 by irradiation with the laser light 703 and the light-absorbing layer 701 is left remained. Another example in which an opening to reach a light-absorbing layer formed below an insulating layer is formed is shown in each of FIGS. 2A to 2D

A light-absorbing layer may also be stacked with a conductive layer (or a semiconductor layer). Further, a plurality of light-absorbing layers may be stacked and/or a plurality of conductive layers may be stacked. FIGS. 2A and 2D show examples in which a stacked layer of a light-absorbing layer and a conductive layer is electrically connected to a conductive film with an insulating layer interposed terebetween. FIGS. 2A to 2D correspond to cross-sectional diagrams taken along line V-X in FIGS. 1A2, 1B2, 1C2, and 1D2, respectively.

In FIGS. 2A to 2D, a conductive material is used as the light-absorbing layer, thereby functioning as a conductive layer. Further, a material which absorbs laser light may be used as the conductive layer formed below the light-absorbing layer, thereby functioning as a light-absorbing layer.

FIG. 2A shows an example in which laser ablation is performed only to an upper portion of a light-absorbing layer below an insulating layer by laser light. A conductive layer 731, a light-absorbing layer 732, and an insulating layer 733 are provided over a substrate 730, and a conductive film 734 is provided in an opening 750 formed in the light-absorbing layer 732 and the insulating layer 733. The light-absorbing layer 732 is exposed at the opening 750 and is in contact with the conductive film 734, thereby electrically connecting each other. A conductive material is used as the light-absorbing layer 732, thereby functioning as a conductive layer. Further, a material which absorbs laser light may be used as the conductive layer 731, thereby functioning as a light-absorbing layer.

The conductive layer 731 and the light-absorbing layer 732 are stacked to form a stacked-layer structure. In this embodiment mode, a low-melting point metal (chromium in this embodiment mode) that is relatively easily evaporated is used for the light-absorbing layer 732, and a high-boiling point (and high-melting point) metal (tungsten in this embodiment mode) that is not easily evaporated compared to the light-absorbing layer 732 is used for the conductive layer 731.

As each of the light-absorbing layer and the conductive layer below the insulating layer, plural kinds of layers having different melting points (boiling points) may be stacked, or of cause, may be a single layer. Examples in which a light-absorbing layer of a single layer is formed below an insulating layer are shown in FIGS. 2B and 2C. FIG. 2B shows an example in which laser ablation is performed to only an upper portion of the light-absorbing layer below the insulating layer by laser light, and FIG. 2C shows an example in which the light-absorbing layer below the insulating layer is removed by laser ablation to expose a substrate 740.

In FIG. 2B, a light-absorbing layer 736 and an insulating layer 738 are provided over a substrate 735, and a conductive film 739 is provided in an opening 751 formed in the light-absorbing layer 736 and the insulating layer 738. In the opening 751, the light-absorbing layer 736 is exposed so as to be in contact with and to electrically connect to the conductive film 739. When only the upper portion in a direction of film thickness of the light-absorbing layer is partially removed as shown in FIGS. 2A and 2B, a laser light irradiation condition (e.g., energy intensity or irradiation period of time) may be controlled or the light-absorbing layer may be formed to be thick.

In FIG. 2C, light-absorbing layers 741 a and 741 b and an insulating layer 743 are provided over the substrate 740, and a conductive film 744 is provided in an opening 752 formed in the insulating layer 743 and the light-absorbing layers 741 a and 741 b. In the opening 752, the light-absorbing layers 741 a and 741 b are exposed so as to be in contact with and to electrically connect to the conductive film 744. Note that as shown in FIG. 2C, the light-absorbing layer and the conductive film are not necessarily in contact with each other on a bottom surface of the opening, and they may be electrically connected to each other by forming the conductive film so as to be in contact with the light-absorbing layer which is exposed on a side surface of the opening.

Further, the opening which functions as contact hole is not limited to a shape in which a side surface is perpendicular to a bottom surface, and may have a shape in which a side of the side surface of the opening is tapered. In FIG. 2D, a conductive layer 746, light-absorbing layers 747 a and 747 b, and an insulating layer 748 are formed over a substrate 745, and an opening 753 is formed in the insulating layer 748 and the light-absorbing layers 747 a and 747 b. For example, the opening 753 may have a mortar shape, in which the side surface of the opening 753 is tapered toward the bottom surface thereof. In the opening 753, the light-absorbing layers 747 a and 747 b are exposed so as to be in contact with and to electrically connect to the conductive film 749.

In this manner, in the opening provided in the insulating layer, the light-absorbing layer below the insulating layer and the conductive film over the insulating layer are electrically connected to each other. The size and shape of the opening formed in the insulating layer can be controlled by a laser light irradiation condition (e.g., energy intensity or irradiation period of time) and properties of materials for the insulating layer and the conductive layer (e.g., thermal conductivity, melting point, and boiling point).

After the opening is formed by laser light irradiation, the conductive material or the insulating material which remains around the opening (a residue in the portion where the conductive layer or the insulating layer is removed) may be washed with a liquid to be removed. In this case, a non-reactive substance such as water may be used for washing, or a chemical solution such as an etchant which reacts with (dissolves) the insulating layer may be used. With an etchant, the opening is over-etched, and dust and the like are removed, so that the surface is further planarized. Further, the opening can also be widened.

Since the opening can be selectively formed by laser light, it is not necessary to form a mask layer, so that the number of steps and materials can be reduced. Further, there are advantages in that the conductive layer and the insulating layer can be processed into a predetermined shape with high precision since laser light can be condensed into an extremely small spot, and the region other than a processed region is not heated substantially since heating is performed for a short period of time and instantaneously.

As described above, an opening (a contact hole) which electrically connects conductive layers can be formed in an insulating layer by laser light irradiation without forming a mask layer using a complicated photolithography process.

Accordingly, by manufacturing a display device according to the present invention, the manufacturing process can be simplified, so that loss of materials and the cost can be reduced. Therefore, display devices can be manufactured with a high yield.

Embodiment Mode 2

In this embodiment mode, a method for forming a contact hole in order to manufacture a display device at low cost through a highly reliable, more simplified process is described with reference to FIGS. 4A1, 4A2, 4B1, 4B2, 4C1, 4C2, 4D1, and 4D2.

In the case where thin films (each of which is a conductive layer or a semiconductor layer) which are stacked with an insulating layer interposed therebetween are electrically connected to each other, an opening (a so-called contact hole) is formed in the insulating layer. In this case, a mask layer is not formed over the insulating layer, and the opening is selectively formed by laser light irradiation. After a light-absorbing layer which absorbs irradiated light is formed and an insulating layer is stacked over the light-absorbing layer, a region at which an opening is to be formed in the stacked layer of the light-absorbing layer and the insulating layer is irradiated with laser light from the insulating layer side. Although the laser light is transmitted through the insulating layer, it is absorbed in the light-absorbing layer. The light-absorbing layer is heated by energy of the absorbed laser light and damages the insulating layer stacked thereover. Accordingly, the opening is formed in the insulating layer, so that the light-absorbing layer below the insulating layer is exposed on a bottom surface of the opening. The light-absorbing layer may evaporate depending on the irradiated energy of laser light. The light-absorbing layer (or a thin film which is stacked below the light-absorbing layer) which is exposed on the bottom surface of the opening may be removed by etching using the insulating layer having the opening as a mask after opening formation by laser light irradiation.

In this embodiment mode using the present invention, since the opening is formed in the upper insulating layer by light absorption of the light-absorbing layer, the opening is formed so as to overlap (be in contact with) the light-absorbing layer in the insulating layer, only at a region which is irradiated with laser light. A region (shape) of the opening formed in the insulating layer reflects not only a shape of a region irradiated with laser light but also a shape of the light-absorbing layer formed therebelow. That is, a region where a formation region of the light-absorbing layer overlaps the region irradiated with laser, light can form an opening region; therefore, openings having various shapes can be formed by controlling the shape of the light-absorbing layer and the region irradiated with laser light (an irradiated spot).

In the case where the light-absorbing layer is formed of a conductive material such as a conductive layer using a conductive material or a semiconductor layer using a semiconductor material, by forming a conductive film in the opening so as to be in contact with the exposed light-absorbing layer, the light-absorbing layer and the conductive film can be electrically connected to each other with the insulating layer interposed therebetween. That is, in the present invention, opening formation in the insulating layer which is formed over the light-absorbing layer which functions as a conductive layer or a semiconductor layer is performed by laser light irradiation to the light-absorbing layer which is selectively formed, so that the opening is formed in the insulating layer above a laser irradiated region of the light-absorbing layer by laser ablation.

Since the opening can be selectively formed by laser light and the light-absorbing layer, it is not necessary to form a mask layer, so that the number of steps and materials can be reduced. Further, there are advantages in that the insulating layer can be processed into a predetermined shape with high precision since laser light can be condensed into an extremely small spot, and the region other than a processed region is not heated substantially since heating is performed for a short period of time and instantaneously.

Specific description is made with reference to FIGS. 4A1, 4A2, 4B1, 4B2, 4C1, 4C2, 4D1, and 4D2. FIGS. 4A2, 4B2, 4C2, and 4D2 are top diagrams each of a conductive layer, and FIGS. 4A1, 4B1, 4C1, and 4D1 are cross-sectional diagrams taken along line Y-Z in FIGS. 4A2, 4B2, 4C2, and 4D2, respectively.

As shown in FIGS. 4A1, 4A2, 4B1, 4B2, 4C1, 4C2, 4D1, and 4D2, light-absorbing layers 301 a and 301 b and an insulating layer 302 are formed over a substrate 300. In this embodiment mode, a conductive material is used as each of the light-absorbing layers 301 a and 301 b, thereby functioning as a conductive layer. In this embodiment mode, chromium is used as the light-absorbing layers 301 aand 301 b. As shown in FIG. 4A2, the light-absorbing layers 301 a and 301 b are selectively formed over the substrate 300 so as not to cover an entire surface of the substrate 300.

As shown in FIG. 4B1, the insulating layer 302, the light-absorbing layers 301 a and 301 b, and the substrate 300 are selectively irradiated with laser light 303 a and 303 b from the insulating layer 302 side. As shown in FIG. 4B2, part of the light-absorbing layers 301 a and 301 b and part of the substrate 300 are irradiated with the laser light 303 a and 303 b to form irradiated regions 304 a and 304 b. By the irradiated energy, the insulating layer 302 only above the irradiated regions of the light-absorbing layers 301 a and 301 b is selectively removed, so that openings 305 a and 305 b can be formed (see FIGS. 4C1 and 4C2). In FIG. 4C1, the insulating layer 302 is separated into insulating layers 306 a, 306 b, 306 c, and 306 d. A conductive film 307 a is formed in the opening 305 a at which the light-absorbing layer 301 a is exposed, thereby electrically connecting to the light-absorbing layer 301 a; and a conductive film 307 b is formed in the opening 305 b at which the light-absorbing layer 301 b is exposed, thereby electrically connecting to the light-absorbing layer 301 b (see FIGS. 4D1 and 4D2).

In this embodiment mode, since the openings 305 a and 305 b are formed in the upper insulating layer 302 by light absorption of the light-absorbing layers 301 a and 301 b, the openings 305 a and 305 b are formed so as to overlap (be in contact with) the light-absorbing layers 301 a and 301 b in the insulating layer 302, only at the regions irradiated with the laser light 303 a and 303 b. Therefore, the opening 305 a is formed in the insulating layer 302 above a region where the light-absorbing layer 301 a overlaps the laser light irradiated region 304 a as shown in FIG. 4C2. On the other hand, the opening 305 b is formed in the insulating layer 302 above a region where the light-absorbing layer 301 b overlaps the laser light irradiated region 304 b. In this embodiment mode, the laser light irradiated regions 304 a and 304 b have the same shape whereas the light-absorbing layers 301 a and 301 b have different shapes. A region (shape) of the opening formed in the insulating layer reflects not only a shape of the laser light irradiated region but also a shape of the light-absorbing layer formed therebelow; therefore, shapes of the openings 305 a and 305 b formed over the light-absorbing layers 301 a and 301 b having the different shapes are different from each other.

That is, a region where a formation region of the light-absorbing layer overlaps the laser light irradiated region can form an opening region; therefore, openings having various shapes can be formed by controlling the shape of the light-absorbing layer and the laser light irradiated region (an irradiated spot). For example, even when a laser beam spot with a large diameter is used, a minute opening with a smaller diameter can be formed by forming the light-absorbing layer selectively. Further, by changing the irradiated region in the light-absorbing layer even when a beam spot having the same shape is used, a plurality of openings having different shapes can be formed. Therefore, various opening shapes can be selected, so that design freedom of a structure of a wiring or the like included in a display device or a semiconductor device is improved.

The light-absorbing layers 301 a and 301 b can be formed by an evaporation method, a sputtering method, a PVD (Physical Vapor Deposition) method, a CVD (Chemical Vapor Deposition) method such as a low-pressure CVD (LPCVD) method or a plasma CVD method, or the like. Further, a method by which a component can be printed or drawn to be a desired pattern, such as various printing methods (a method for forming a component to be a desired pattern, e.g., screen (mimeograph) printing, offset (planograph) printing, relief printing, or gravure (intaglio) printing), a dispenser method, a selective-coating method, or the like can also be used.

As the light-absorbing layers 301 a and 301 b, one or a plurality of kinds of chromium, molybdenum, nickel, titanium, cobalt, copper, tungsten, and aluminum can be used. Further, indium tin oxide (ITO), indium tin oxide containing silicon oxide (ITSO), zinc oxide (ZnO), indium tin oxide containing silicon oxide, a conductive material in which zinc oxide is doped with gallium (Ga), or indium zinc oxide (IZO) may also be used. Further, a semiconductor material can also be used as each of the light-absorbing layers. For example, an inorganic semiconductor material such as silicon, germanium, silicon germanium, arsenic gallium, molybdenum oxide, tin oxide, bismuth oxide, vanadium oxide, nickel oxide, zinc oxide, gallium arsenide, gallium nitride, indium oxide, indium phosphide, indium nitride, cadmium sulfide, cadmium telluride, or strontium titanate can be used. Further, hydrogen or an inert gas (e.g., helium (He), argon (Ar), krypton (Kr), neon (Ne), or xenon (Xe)) may also be added to each of the light-absorbing layers. The insulating layer in which the opening is formed can be formed of a material which transmits laser light, such as a light-transmitting inorganic insulating material, an organic resin, or the like.

In this manner, in the opening provided in the insulating layer, the light-absorbing layer below the insulating layer and the conductive film over the insulating layer are electrically connected to each other. The size and shape of the opening formed in the insulating layer can be controlled by a laser light irradiation condition (e.g., energy intensity or irradiation period of time) and properties of materials for the insulating layer and the conductive layer (e.g., thermal conductivity, melting point, and boiling point).

After the opening is formed by laser light irradiation, the conductive material or the insulating material which remains around the opening (a residue in the portion where the conductive layer or the insulating layer is removed) may be washed with a liquid to be removed. In this case, a non-reactive substance such as water may be used for washing, or a chemical solution such as an etchant which reacts with (dissolves) the insulating layer may be used. With an etchant, the opening is over-etched, and dust and the like are removed, so that the surface is further planarized. Further, the opening can also be widened.

Since the opening can be selectively formed by laser light, it is not necessary to form a mask layer, so that the number of steps and materials can be reduced. Further, there are advantages in that the conductive film and the insulating layer can be processed into predetermined shapes with high precision since laser light can be condensed into an extremely small spot, and the region other than a processed region is not heated substantially since heating is performed for a short period of time and instantaneously.

As described above, an opening (a contact hole) which electrically connects conductive layers can be formed in an insulating layer by laser light irradiation without forming a mask layer using a complicated photolithography process.

Accordingly, by manufacturing a display device according to the present invention, the manufacturing process can be simplified, so that loss of materials and the cost can be reduced. Therefore, display devices can be manufactured with a high yield.

Embodiment Mode 3

In this embodiment mode, a method for manufacturing a display device in order to manufacture the display device at low cost through a highly reliable, more simplified process is described with reference to FIGS. 3A to 3C.

In this embodiment mode, components (also called patterns) such as a conductive layer, a semiconductor layer, or the like are selectively formed to have desired shapes without using a photolithography process in processing a thin film into a desired pattern. In the present invention, the components (also called the patterns) mean a conductive layer such as a wiring layer, a gate electrode layer, a source electrode layer, or a drain electrode layer, a semiconductor layer, a mask layer, an insulating layer, or the like included in a thin film transistor or a display device and include all component parts formed to have predetermined shapes.

In this embodiment mode, a light-absorbing film such as a conductive film or a semiconductor film is formed over a light-transmitting transposing substrate and the transposing substrate side is irradiated with laser light, so that the light-absorbing film corresponding to a laser light irradiated region is printed on a transposed substrate, thereby forming a light-absorbing layer such as a conductive layer or a semiconductor layer with a desired shape (pattern). In this specification, the substrate over which the light-absorbing film such as the conductive film or the semiconductor film is formed and which is irradiated with laser light in the first step is referred to as the transposing substrate, and the substrate over which the light-absorbing layer such as the conductive layer or the semiconductor layer is selectively formed finally is referred to as the transposed substrate. Since the light-absorbing film such as the conductive film or the semiconductor film can be selectively formed to have a desired shape without using a photolithography process, the manufacturing process can be simplified and cost can be reduced, for example.

A method for forming a thin film described in this embodiment mode is described in detail with reference to FIGS. 3A to 3C. In FIGS. 3A to 3C, a light-absorbing film 2202 is formed over a first substrate 2201 which is a transposing substrate, and the first substrate 2201 and a second substrate 2200 which is a transposed substrate are disposed so as to interpose the light-absorbing film 2202 therebetween.

Laser light 2203 is transmitted through the substrate 2201 to selectively irradiate the light-absorbing film 2202 from the substrate 2201 side. The light-absorbing film 2202 in a region irradiated with the laser light 2203 absorbs the laser light 2203 and is printed on the second substrate 2200 side as a light-absorbing layer 2205 by energy of the heat or the like. On the other hand, the other region which is not irradiated with the laser light 2203 is left remained on the first substrate 2201 side as light-absorbing films 2204 a and 2204 b. In this manner, when processing a thin film which is a light-absorbing layer 2206 into a desired pattern, without using a photolithography process, a component (also called a pattern) such as a conductive layer or a semiconductor layer is selectively formed to have a desired shape.

As for the laser light, similar laser light to Embodiment Mode 1 can be used and similar irradiation to the same can be performed, and the laser irradiation writing system shown in FIG. 30 may be used. Therefore, specific description thereof is omitted here.

After being transposed by the laser light, the light-absorbing layer may be subjected to heat treatment or may be irradiated with laser light.

A material which absorbs irradiated light is used for the light-absorbing film 2202 which is an object to be transposed, and a light transmitting substrate which transmits irradiated light is used for the first substrate 2201. By the present invention, transposition can be freely performed to various substrates; therefore, the range of selectable materials of the transposed substrate is increased. Further, an inexpensive material can be selected for the transposed substrate, so that a display device can be manufactured at low cost as well as the display device can have various functions in accordance with use application.

The thin film formation method in this embodiment mode can be used for forming a conductive layer such as a wiring layer, a gate electrode layer, a source electrode layer, or a drain electrode layer, a semiconductor layer, a mask layer, an insulating layer, or the like included in a thin film transistor or a display device. A film using a desired material may be formed as a light-absorbing layer, and light which is absorbed in the film may be selected and used for light irradiation.

For example, a conductive material can be used as the light-absorbing layer. For example, one or a plurality of kinds of chromium, tantalum, silver, molybdenum, nickel, titanium, cobalt, copper, and aluminum can be used. Further, indium tin oxide (ITO), indium tin oxide containing silicon oxide (ITSO), zinc oxide (ZnO), indium tin oxide containing silicon oxide, a conductive material in which zinc oxide is doped with gallium (Ga), or indium zinc oxide (IZO) may also be used. Alternatively, a semiconductor material can be used as the light-absorbing layer. For example, an inorganic semiconductor material such as silicon, germanium, silicon germanium, gallium arsenide, molybdenum oxide, tin oxide, bismuth oxide, vanadium oxide, nickel oxide, gallium arsenide, gallium nitride, indium oxide, indium phosphide, indium nitride, cadmium sulfide, cadmium telluride, or strontium titanate can be used. The light-absorbing layer may also be added with hydrogen or an inert gas (e.g., helium (He), argon (Ar), krypton (Kr), neon (Ne), or xenon (Xe)).

By the present invention, components such as a wiring included in a display device can be formed to have desired shapes. Further, a display device can be manufactured through a simplified process with a complicated photolithography process reduced, so that loss of materials and the cost can be reduced. Therefore, high performance and highly reliable display devices can be manufactured with a high yield.

Embodiment Mode 4

FIG. 25A is a top diagram showing a structure of a display panel of the present invention, in which a pixel portion 2701 in which pixels 2702 are arranged in matrix, a scan line input terminal 2703, and a signal line input terminal 2704 are formed over a substrate 2700 having an insulating surface. The number of pixels may be set according to various standards: the number of pixels of XGA for RGB full-color display may be 1024×768×3 (RGB), that of XGA for RGB full-color display may be 1600×1200×3 (RGB), and that corresponding to a full-spec high vision for RGB full-color display may be 1920×1080×3 (RGB).

Scan lines extended from the scan line input terminal 2703 intersect signal lines extended from the signal line input terminal 2704, and the pixels 2702 are arranged in matrix at intersections. Each pixel 2702 is provided with a switching element and a pixel electrode connected to the switching element. A typical example of the switching element is a TFT. A gate electrode side of the TFT is connected to the scan line, and a source or drain side thereof is connected to the signal line, so that each pixel can be controlled independently by signals inputted from outside.

Although FIG. 25A shows the structure of the display panel in which signals inputted to the scan and signal lines are controlled by an external driver circuit, driver ICs 2751 may be mounted on the substrate 2700 by a COG (Chip On Glass) method as shown in FIG. 26A. Further, the driver ICs may also be mounted by a TAB (Tape Automated Bonding) method as shown in FIG. 26B. The driver ICs may be either ones formed using a single crystalline semiconductor substrate or circuits that are formed using a TFT over a glass substrate. In FIGS. 26A and 26B, each driver IC 2751 is connected to an FPC 2750.

Further, in the case where a TFT provided in each pixel is formed using a polycrystalline (microcrystalline) semiconductor having high crystallinity, a scan line driver circuit 3702 may be formed over a substrate 3700 as shown in FIG. 25B. In FIG. 25B, reference numeral 3701 denotes a pixel portion. A signal line driver circuit is controlled by an external driver circuit, which is similar to FIG. 25A. In the case where, like the TFT formed in the present invention, a TFT provided in each pixel is formed using a polycrystalline (microcrystalline) semiconductor, a single crystalline semiconductor, or the like with high mobility, a scan line driver circuit 4702 and a signal line driver circuit 4704 can be formed over the same substrate 4700 as a pixel region 4701, as shown in FIG. 25C.

An embodiment mode of the present invention is described with reference to FIGS. 8A to 8C, 9A to 9C, 10A to 10C, 11A to 11C, 12A to 12C, and 13A and 13B. Specifically, a method for manufacturing a display device including an inversely staggered thin film transistor, to which the present invention is applied is described. FIG. 8A, 9A, 10A, 11A, and 12A are top diagrams each of a pixel portion of a display device; FIG. 8B, 9B, 10B, 11B, and 12B are cross-sectional diagrams taken along line A-C in FIG. 8A, 9A, 10A, 11A, and 12A, respectively; and FIG. 8C, 9C, 10C, 11C, and 12C are cross-sectional diagrams taken along line B-D in FIG. 8A, 9A, 10A, 11A, and 12A, respectively. FIGS. 13A and 13B are also cross-sectional diagrams of the display device.

As a substrate 100, a glass substrate made of barium borosilicate glass, aluminoborosilicate glass, or the like; a quartz substrate; a metal substrate; or a plastic substrate having heat resistance that can withstand process temperature of the manufacturing process is used. Further, the surface of the substrate 100 may be polished by a CMP method or the like so as to be planarized. Note that an insulating layer may be formed over the substrate 100. The insulating layer may be formed of either a single layer or a stacked layer using an oxide material containing silicon or a nitride material containing silicon by various methods such as a CVD method including a plasma CVD method, a sputtering method, or a spin coating method. Although this insulating layer is not necessarily formed, it has an advantageous effect of blocking contaminants and the like from the substrate 100.

Gate electrode layers 103 and 104 (104 a and 104 b) are formed over the substrate 100. Each of the gate electrode layers 103 and 104 (104 a and 104 b) may be formed of an element selected from silver, gold, nickel, platinum, lead, iridium, rhodium, tantalum, tungsten, titanium, molybdenum, aluminum, and copper, or an alloy material or a compound material containing the above element as its main component. Further, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus, or an alloy containing silver, lead, and copper may be used. Further, a single-layer structure or a structure including a plurality of layers may be used. For example, a two-layer structure of a tungsten nitride film and a molybdenum film or a three-layer structure in which a tungsten film with a thickness of 50 nm, an alloy film of aluminum and silicon with a thickness of 500 nm, and a titanium nitride film with a thickness of 30 nm are sequentially stacked may be used. In the case of the three-layer structure, tungsten nitride may be used instead of tungsten of the first conductive film, an alloy film of aluminum and titanium may be used instead of the alloy film of aluminum and silicon of the second conductive film, and a titanium film may be used instead of the titanium nitride film of the third conductive film.

The gate electrode layers 103, 104 a, and 104 b can be formed by using a sputtering method, a PVD (Physical Vapor Deposition) method, a CVD (Chemical Vapor Deposition) method such as a low-pressure CVD (LPCVD) method or a plasma CVD method, or the like, and processing using a mask layer. Further, a method by which a component can be transferred or drawn to be a desired pattern, such as various printing methods (a method for forming a component to be a desired pattern, e.g., screen (mimeograph) printing, offset (planograph) printing, relief printing, or gravure (intaglio) printing), a droplet discharging method, a dispenser method, a selective-coating method, or the like can also be used.

A conductive film may be processed by dry etching or wet etching. By using an ICP (Inductively Coupled Plasma) etching method and adjusting an etching condition (e.g., the amount of power applied to a coiled electrode, the amount of power applied to an electrode on a substrate side, or the electrode temperature on the substrate side) as appropriate, each electrode layer can be etched into a tapered shape. Note that as an etching gas, a chlorine-based gas such as Cl₂, BCl₃, SiCl₄, or CCl₄, a fluorine-based gas such as CF₄, SF₆, or NF₃, or O₂ can be used as appropriate.

Further, as for formation of each gate electrode layer, after a conductive film which is a light-absorbing film is formed over a transposing substrate, the gate electrode layer is selectively formed over a transposed substrate by laser light by being processed into a desired shape. After being transposed by the laser light, the light-absorbing layer may be subjected to heat treatment or may be irradiated with laser light.

A material which absorbs irradiated light is used for the light-absorbing film which is an object to be transposed, and a light transmitting substrate which transmits irradiated light is used for the transposing substrate. By the present invention, transposition can be freely performed to various substrates; therefore, the range of selectable materials of the transposed substrate is increased. Further, an inexpensive material can be selected for the transposed substrate, so that a display device can be manufactured at low cost as well as the display device can have various functions in accordance with use application.

Next, a gate insulating layer 105 is formed over the gate electrode layers 103 and 104 (104 a and 104 b) (see FIGS. 8A to 8C). The gate insulating layer 105 may be formed of an oxide material of silicon, a nitride material of silicon, or the like, and either a single-layer structure or a stacked-layer structure may be employed. In this embodiment mode, a two-layer structure of a silicon nitride film and a silicon oxide film is used. Alternatively, a single layer of a silicon oxynitride film or a stacked layer including three or more layers may be used. Preferably, a silicon nitride film having dense film quality is used. Further, in the case where silver, copper, or the like is used for each conductive layer formed by a droplet discharging method, an effect of preventing impurity diffusion and planarizing the surface can be obtained by forming a silicon nitride film or a NiB film as a barrier film thereover. Note that in order to form a dense insulating film with less gate leakage current at a low deposition temperature, a rare gas element such as argon may be mixed into the insulating film by being contained in a reaction gas.

Next, a semiconductor layer is formed. A semiconductor layer having one conductivity type may be formed as needed. Further, an NMOS structure of an n-channel TFT in which a semiconductor layer having n-type conductivity is formed, a PMOS structure of a p-channel TFT in which a semiconductor layer having p-type conductivity is formed, or a CMOS structure of an n-channel TFT and a p-channel TFT can be manufactured. Further, in order to impart conductivity type, an element which provides conductivity type may be added to a semiconductor layer by doping to form an impurity region in the semiconductor layer, so that an n-channel TFT or a p-channel TFT can be formed. Instead of forming a semiconductor layer having n-type conductivity, plasma treatment with a PH₃ gas may be performed, to provide conductivity type for a semiconductor layer.

As a material for forming the semiconductor layer, the following can be used: an amorphous semiconductor (hereinafter also referred to as an “AS”) formed by a vapor deposition method using a semiconductor material gas typified by silane or germane or a sputtering method; a polycrystalline semiconductor or a semi-amorphous semiconductor (also referred to as microcrystal and hereinafter also referred to as a “SAS”) formed by crystallizing the amorphous semiconductor by using light energy or thermal energy; or the like. The semiconductor layer can be formed by various methods (e.g., a sputtering method, an LPCVD method, or a plasma CVD method).

An SAS is a semiconductor having an intermediate structure between amorphous and crystalline (including single crystal and polycrystalline) structures and a third state which is stable in free energy. Further, an SAS includes a crystalline region with a short-distance order and lattice distortion. A crystal grain having a diameter of 0.5 to 20 nm can be observed at least in part of the film. In the case where silicon is contained as a main component, Raman spectrum is shifted toward the low-frequency side than 520 cm⁻¹. The diffraction peaks of (111) and (220), which are considered to be derived from a silicon crystal lattice, are observed by X-ray diffraction. An SAS contains hydrogen or halogen at 1 atomic % or more in order to terminate dangling bonds. An SAS is formed by glow discharge decomposition (plasma CVD) of a gas containing silicon. As the gas containing silicon, as well as SiH₄, any of Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄, or the like can be used. Further, F₂ or GeF₄ may be mixed. The gas containing silicon may be diluted with H₂, or H₂ and one or a plurality of kinds of rare gas elements of He, Ar, Kr, and Ne. The dilution ratio is in the range of 1:2 to 1:1000, pressure is approximately 0.1-133 Pa, and a power source frequency is 1-120 MHz, preferably 13-60 MHz. A temperature for heating the substrate is preferably less than or equal to 300° C., and an SAS can also be formed at 100-200° C. It is preferable that the concentration of impurities of atmospheric components such as oxygen, nitrogen, and carbon as impurity elements in the film be less than or equal to 1×10²⁰ cm⁻³. In particular, an oxygen concentration is preferably less than or equal to 5×10¹⁹/cm⁻³, and more preferably less than or equal to 1×1¹⁹/cm⁻³. Further, when a rare gas element such as helium, argon, krypton, or neon is contained to further increase the lattice distortion, stability can be enhanced, and a favorable SAS can be obtained. Further, as the semiconductor layer, a stacked layer in which an SAS layer formed by using a hydrogen-based gas is stacked over an SAS layer formed by using a fluorine-based gas may be used.

As a typical example of an amorphous semiconductor, hydrogenated amorphous silicon can be given; and as a typical example of a crystalline semiconductor, polysilicon or the like can be given. Polysilicon (polycrystalline silicon) includes so-called high-temperature polysilicon formed using polysilicon as a main material which is formed at a processing temperature of more than or equal to 800° C., so-called low-temperature polysilicon formed using polysilicon as a main material which is formed at a processing temperature of less than or equal to 600° C., polysilicon crystallized by adding an element which promotes crystallization, and the like. Of course, as described above, a semi-amorphous semiconductor or a semiconductor which includes a crystalline phase in part of the film can also be used.

When a crystalline semiconductor layer is used as the semiconductor layer, the crystalline semiconductor layer may be formed by various methods (e.g., a laser crystallization method, a thermal crystallization method, or a thermal crystallization method using an element such as nickel which promotes crystallization). Further, a microcrystalline semiconductor that is an SAS may be crystallized by laser irradiation to enhance the crystallinity. In the case where the element which promotes crystallization is not used, before the amorphous silicon film is irradiated with laser light, the amorphous silicon film is heated at 500° C. for one hour in a nitrogen atmosphere to discharge hydrogen until the hydrogen concentration in the amorphous silicon film becomes less than or equal to 1×10²⁰ atoms/cm³. This is because, if the amorphous silicon film containing much hydrogen is irradiated with laser light, the amorphous silicon film would be broken.

A method for introducing a metal element into the amorphous semiconductor layer is not particularly limited as long as the metal element can be introduced into a surface of or inside the amorphous semiconductor layer. For example, a sputtering method, a CVD method, a plasma treatment method (including a plasma CVD method), an adsorption method, or a method for applying a solution of metal salt can be used. Among them, a method using a solution is simple and advantageous in that the concentration of the metal element can be easily controlled. At this time, it is desirable to form an oxide film by UV light irradiation in an oxygen atmosphere, a thermal oxidation method, treatment with either ozone water containing hydroxyl radicals or hydrogen peroxide, or the like to improve wettability of the surface of the amorphous semiconductor layer so that an aqueous solution is diffused on the entire surface of the amorphous semiconductor layer.

For crystallizing the amorphous semiconductor layer, heat treatment may be combined with laser light irradiation, or either one of heat treatment and laser light irradiation may be performed plural times.

Alternatively, a crystalline semiconductor layer may be directly formed over the substrate by a plasma method.

An organic semiconductor material may be used as a semiconductor, and a printing method, a dispenser method, a spray method, a spin coating method, a droplet discharging method, or the like can be used. In this case, since the above-described etching step is not necessary, the number of steps can be reduced. As the organic semiconductor, a low-molecular material, a high-molecular material, or the like can be used. Further, an organic coloring matter, a conductive high-molecular material, or the like can also be used. As the organic semiconductor material used in the present invention, a π-electron conjugated high-molecular material of which skeleton includes a conjugated double bond is desirable. Typically, a soluble high-molecular material such as polythiophene, polyfluorene, poly(3-alkylthiophene), or a polythiophene derivative can be used.

Further, as the organic semiconductor material which can be used in the present invention, there is a material by which a semiconductor layer can be formed by depositing a soluble precursor thereof to form a film and processing it. Note that as examples of such an organic semiconductor material, there are polythienylenevinylene, poly(2,5-thienylenevinylene), polyacetylene, polyacetylene derivatives, polyallylenevinylene, and the like.

In order to change the precursor into the organic semiconductor, not only heat treatment but also addition of a reaction catalyst such as a hydrogen chloride gas is performed. Further, as a typical solvent for dissolving the soluble organic semiconductor material, the following can be used: toluene, xylene, chlorobenzene, dichlorobenzene, anisole, chloroform, dichloromethane, γbutyllactone, butylcellosolve, cyclohexane, NMP (N-methyl-2-pyrrolidone), cyclohexanone, 2-butanon, dioxane, dimethylformamide (DMF), THF (tetrahydrofuran), or the like.

In this embodiment mode, amorphous semiconductor layers are formed as semiconductor layers 108 and 109 and semiconductor layers having one conductivity type 110 and 111. In this embodiment mode, a semiconductor film having n-type conductivity containing phosphorus (P) which is an impurity element imparting n-type conductivity is formed as each semiconductor film having one conductivity type. Each semiconductor film having one conductivity type functions as a source or drain region. Each semiconductor film having one conductivity type may be formed as needed, and a semiconductor film having n-type conductivity containing an impurity element imparting n-type conductivity (P or As) or a semiconductor film having p-type conductivity containing an impurity element imparting p-type conductivity (B) can be formed.

Next, an opening 107 is formed in the gate insulating layer 105. A mask layer is formed of an insulator such as resist or polyimide. The opening 107 is formed in part of the gate insulating layer 105 by etching using the mask layer, so that part of the gate electrode layer 104 a provided below the gate insulating layer 105 can be exposed. Although either plasma etching (dry etching) or wet etching may be employed for the etching, plasma etching is suitable to process a large substrate. As an etching gas, a fluorine-based or chlorine-based gas such as CF₄, NF₃, Cl₂, or BCl₃ is used. An inert gas such as He or Ar may be added as needed. Further, by employing an etching process using atmospheric discharge plasma, a local discharge process can also be performed, so that a mask layer does not need to be formed over an entire surface of a substrate.

In this embodiment mode, the opening 107 is formed by laser light as described in Embodiment Mode 1 (see FIGS. 9A to 9C). The gate electrode layer 104 a which is a light-absorbing layer is irradiated with laser light 113 from the gate insulating layer 105 side, and the gate insulating layer 105 above an irradiated region of the gate electrode layer 104 a is removed by irradiated energy, so that the opening 107 can be formed. In this embodiment mode, since the opening is formed in the upper insulating layer by light absorption of the light-absorbing layer, the opening is formed so as to overlap (be in contact with) the light-absorbing layer in the insulating layer, only at a region which is irradiated with laser light. A region (shape) of the opening formed in the insulating layer reflects not only a shape of a region irradiated with laser light but also a shape of the light-absorbing layer formed therebelow. That is, a region where a formation region of the light-absorbing layer overlaps the region irradiated with laser light can form an opening region; therefore, openings having various shapes can be formed by controlling the shape of the light-absorbing layer and the region irradiated with laser light (an irradiated spot).

A conductive film forming a source or drain electrode layer is formed in the opening 107 where the gate electrode layer 104 a is exposed, thereby the gate electrode layer 104 a and the source or drain electrode layer can be electrically connected to each other. The opening 107 may be formed after formation of the semiconductor layer.

Next, source or drain electrode layers 116, 117, 118, and 119 are formed. For the source or drain electrode layers 116, 117, 118, and 119, an element selected from Ag (silver), Au (gold), Cu (copper), W (tungsten), Al (aluminum), Mo (molybdenum), Ta (tantalum), and Ti (titanium), an alloy material or a compound material containing the above element as its main component, or the like can be used. Further, indium tin oxide (ITO), indium tin oxide containing silicon oxide (ITSO), organic indium, organic tin, zinc oxide, titanium nitride, or the like, having a light-transmitting property may be combined.

The source or drain electrode layers 116, 117, 118, and 119 can be formed by a sputtering method, a PVD (Physical Vapor Deposition) method, a CVD (Chemical Vapor Deposition) method such as a low-pressure CVD (LPCVD) method or a plasma CVD method, or the like and processing using a mask layer. Further, a method by which a component can be transferred or drawn to be a desired pattern, such as various printing methods (a method for forming a component to be a desired pattern, e.g., screen (mimeograph) printing, offset (planograph) printing, relief printing, or gravure (intaglio) printing), a droplet discharging method, a dispenser method, a selective-coating method, or the like can also be used.

The conductive film may be processed by dry etching or wet etching. By using an ICP (Inductively Coupled Plasma) etching method and adjusting an etching condition (e.g., the amount of power applied to a coiled electrode, the amount of power applied to an electrode on a substrate side, or the electrode temperature on the substrate side) as appropriate, the electrode layer can be etched into a tapered shape. Note that as an etching gas, a chlorine-based gas such as Cl₂, BCl₃, SiCl₄, or CCl₄, a fluorine-based gas such as CF₄, SF₆, or NF₃, or O₂ can be used as appropriate.

The source or drain electrode layers may be formed as follows: a conductive film which is a light-absorbing film is formed over a transposing substrate, and printed on a transposed substrate selectively while being processed into a desired shape by laser light.

The source or drain electrode layer 116 also functions as a source wiring layer, and the source or drain electrode layer 118 also functions as a power source line.

In the opening 107 formed in the gate insulating layer 105, the source or drain electrode layer 117 and the gate electrode layer 104 a are electrically connected to each other. Part of the source or drain electrode layer 118 forms a capacitor. After the source or drain electrode layers 116, 117, 118, and 119 are formed, the semiconductor layers 108 and 109 and the semiconductor layers having one conductivity type 110 and 111 are processed into desired shapes. In this embodiment mode, the semiconductor layers 108 and 109 and the semiconductor layers having one conductivity type 110 and 111 are processed by using the source or drain electrode layers 116, 117, 118, and 119 as masks, thereby forming semiconductor layers 114 and 115 and semiconductor layers having one conductivity type 120 a, 120 b, 121 a, and 121 b.

Through the above-described process, transistors 139 a and 139 b which are inversely staggered thin film transistors are manufactured (see FIGS. 10A to 10C).

An insulating layer 123 is formed over the gate insulating layer 105 and the transistors 139 a and 139 b.

The insulating layer 123 can be formed by a sputtering method, a PVD (Physical Vapor Deposition) method, a CVD (Chemical Vapor Deposition) method such as a low-pressure CVD (LPCVD) method or a plasma CVD method, or the like. Further, a droplet discharging method, various printing methods (a method for forming a pattern, such as screen printing or offset printing), a coating method such as a spin-coating method, a dipping method, a dispenser method, or the like may also be used.

The insulating layer 123 can be formed of a material selected from silicon oxide, silicon nitride, silicon oxinitride, aluminum oxide, aluminum nitride, aluminum oxynitride, diamond-like carbon (DLC), nitrogen-containing carbon (CN), polysilazane, and other substances containing an inorganic insulating material. Further, a material containing siloxane may be used. Further alternatively, an organic insulating material such as polyimide, acrylic, polyamide, polyimide amide, resist, or benzocyclobutene can be used. Further alternatively, an oxazole resin can be used, and for example, photocurable polybenzoxazole or the like can be used.

Next, an opening 125 is formed in the insulating layer 123. In this embodiment mode, as described in Embodiment Mode 1, the opening 125 is formed by laser light. The source or drain electrode layer 119 is selectively irradiated with laser light 124 from the gate insulating layer 123 side, and the gate insulating layer 123 above an irradiated region of the source or drain electrode layer 119 is removed by irradiated energy, so that the opening 125 can be formed (see FIGS. 11A to 11C). In this embodiment mode, since the opening is formed in the upper insulating layer by light absorption of the light-absorbing layer, the opening is formed so as to overlap (be in contact with) the light-absorbing layer in the insulating layer, only at a region which is irradiated with laser light. A region (shape) of the opening formed in the insulating layer reflects not only a shape of a region irradiated with laser light but also a shape of the light-absorbing layer formed therebelow. That is, a region where a formation region of the light-absorbing layer overlaps the region irradiated with laser light can form an opening region; therefore, openings having various shapes can be formed by controlling the shape of the light-absorbing layer and the region irradiated with laser light (an irradiated spot).

A first electrode layer 126 of a light-emitting element, which functions as a pixel electrode is formed in the opening 125 where the source or drain electrode layer 119 is exposed, thereby the source or drain electrode layer 119 and the first electrode layer 126 can be electrically connected to each other (see FIGS. 12A to 12C).

The first electrode layer 126 may also be formed as follows, as described in Embodiment Mode 3: a conductive light-absorbing film is formed over a transposing substrate and irradiated with laser light, so as to be formed selectively over a transposed substrate while being processed into a desired shape.

In this embodiment mode, the first electrode layer is formed by forming a conductive film and processing into a desired shape by using a mask layer.

The first electrode layer 126 can be formed by a sputtering method, a PVD (Physical Vapor Deposition) method, a CVD method such as a low-pressure CVD (LPCVD) method or a plasma CVD method, or the like. As a conductive material to form the first electrode layer 126, indium tin oxide (ITO), indium tin oxide containing silicon oxide (ITSO), zinc oxide (ZnO), or the like can be used. Preferably, indium tin oxide containing silicon oxide is used by a sputtering method using a target in which silicon oxide is contained at 2 to 10 wt % in ITO. Instead, a conductive material in which ZnO is doped with gallium (Ga) or indium zinc oxide (IZO) which is an oxide conductive material containing silicon oxide, formed using a target in which indium oxide is doped with zinc oxide (ZnO) at 2 to 20 wt % may be used.

As a mask layer, a resin material such as an epoxy resin, a phenol resin, a novolac resin, an acrylic resin, a melamine resin, a urethane resin, or the like is used. Further, the mask layer may be formed by a droplet discharging method using an organic material such as benzocyclobutene, parylene, fluorinated arylene ether, or polyimide having a light-transmitting property; a compound material formed by polymerization of a siloxane-based polymer or the like; a composition material containing water-soluble homopolymer and water-soluble copolymer; or the like. Alternatively, a commercial resist material containing photosensitizer may be used. For example, a positive type resist or a negative type resist may be used. In using any material, the surface tension and the viscosity are appropriately controlled by, for example, controlling the concentration of a solvent or by adding a surfactant or the like.

The first electrode layer 126 may be processed by dry etching or wet etching. By using an ICP (Inductively Coupled Plasma) etching method and controlling as appropriate an etching condition (e.g., the amount of power applied to a coiled electrode, the amount of power applied to an electrode on a substrate side, or the electrode temperature on the substrate side), the electrode layer can be etched into a tapered shape. Note that as an etching gas, a chlorine-based gas such as Cl₂, BCl₃, SiCl₄, or CCl₄, a fluorine-based gas such as CF₄, SF₆, or NF₃, or O₂ can be used as appropriate.

The first electrode layer 126 may be cleaned and polished by a CMP method or using a polyvinyl-alcohol-based porous body so as to planarize the surface thereof. Further, after being polished using a CMP method, the surface of the first electrode layer 126 may be subjected to ultraviolet light irradiation, oxygen plasma treatment, or the like.

Through the above-described process, a TFT substrate for a display panel in which a bottom-gate TFT and the first electrode layer 126 are connected over the substrate 100 is completed. The TFT in this embodiment mode is inversely staggered type.

Next, an insulating layer 131 (also called a partition wall) is selectively formed. The insulating layer 131 is formed so as to have an opening over the first electrode layer 126. In this embodiment mode, the insulating layer 131 is formed over the entire surface and patterned by etching using a mask of a resist or the like. When the insulating layer 131 is formed by a droplet discharging method, a printing method, a dispenser method, or the like by which the pattern can be formed directly and selectively, patterning by etching is not necessarily carried out.

The insulating layer 131 can be formed using an inorganic insulating material such as silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, or aluminum oxynitride; an acrylic acid, a methacrylic acid, or a derivative thereof; a heat-resistant high-molecular material such as polyimide, aromatic polyamide, or polybenzimidazole; an insulating material of inorganic siloxane which includes a Si—O—Si bond among compounds formed using a siloxane-based material as a starting material and which include silicon, oxygen, and hydrogen; or an insulating material of organic siloxane of which hydrogen bonded to silicon is substituted by an organic group such as methyl or phenyl. A photosensitive or nonphotosensitive material such as acrylic or polyimide may also be used. The insulating layer 131 is preferably formed to have a continuously-changing radius of curvature, so that the coverage with an electroluminescent layer 132 and a second electrode layer 133 which are formed over the insulating layer 131 improves.

Further, after the insulating layer 131 is formed by discharging a composition by a droplet discharging method, a surface thereof may be planarized by pressing with pressure to enhance the planarity. As a pressing method, concavity and convexity of the surface may be reduced by scanning the surface with a roller-shaped object, or the surface may be pressed perpendicularly with a flat plate-shaped object. Alternatively, concavity and convexity of the surface may be removed with an air knife after the surface is softened or melted with a solvent or the like. Further, a CMP method may also be used for polishing the surface. This step can be employed in planarizing the surface when the surface becomes uneven due to a droplet discharging method. When the planarity is enhanced by this step, display irregularity of the display panel or the like can be prevented, and thus, a high precision image can be displayed.

A light-emitting element is formed over the substrate 100 which is the TFT substrate for the display panel (see FIGS. 13A and 13B).

Before the electroluminescent layer 132 is formed, heat treatment is performed at 200° C. in the atmospheric pressure to remove moisture in the first electrode layer 126 and the insulating layer 131 and moisture adsorbed on their surfaces. Further, it is preferable to perform the heat treatment at 200-400° C., more preferably 250-350° C., under low pressure and to form the electroluminescent layer 132 successively without exposing the substrate to the air by a vacuum evaporation method or a droplet discharging method under low pressure.

As the electroluminescent layer 132, materials exhibiting light of red (R), green (G), and blue (B) are selectively deposited by an evaporation method using an evaporation mask, or the like. The materials exhibiting light of red (R), green (G), and blue (B) can also be deposited by a droplet discharging method (by using a low-molecular material, a high-molecular material, or the like) similarly to a color filter, and in this case, materials for R, G and B can be selectively deposited without using a mask, which is preferable. The second electrode layer 133 is stacked over the electroluminescent layer 132, so that a display device having a display function using a light-emitting element is completed.

Although not shown in the drawing, it is effective to provide a passivation film so as to cover the second electrode layer 133. The passivation (protection) film provided in manufacturing a display device may employ a single-layer structure or a multilayer structure. The passivation film can be formed of a single layer or a stacked layer of an insulating film containing silicon nitride (SiN), silicon oxide (SiO₂), silicon oxynitride (SiON), silicon nitride oxide (SiNO), aluminum nitride (AIN), aluminum oxynitride (AION), aluminum nitride oxide containing more nitrogen than oxygen (AINO), aluminum oxide, diamond-like carbon (DLC), or carbon-containing nitrogen. For example, a stacked layer of a carbon-containing nitrogen or silicon nitride, or an organic material can also be used, and a stacked layer of a high-molecular material such as styrene polymer may also be used. Alternatively, a siloxane material may be used.

At this time, it is preferable to use a film with which favorable coverage is provided as the passivation film, and it is effective to use a carbon film, particularly a DLC film as the passivation film. A DLC film, which can be formed in the temperature range from room temperature to less than or equal to 100° C., can be formed easily even over an electroluminescent layer having a low heat resistance. A DLC film can be formed by a plasma CVD method (typically, an RF plasma CVD method, a microwave CVD method, an electron cyclotron resonance (ECR) CVD method, a heat filament CVD method, or the like), a combustion method, a sputtering method, an ion beam evaporation method, a laser evaporation method, or the like. As a reaction gas for deposition, a hydrogen gas and a hydrocarbon-based gas (e.g., CH₄, C₂H₂, or C₆H₆) are used to be ionized by glow discharge, and the ions are accelerated to impact against a cathode to which negative self-bias voltage is applied. Further, a CN film may be formed using a C₂H₄ gas and a N₂ gas as reaction gases. A DLC film, which has high blocking effect against oxygen, can suppress oxidization of the electroluminescent layer. Accordingly, a problem such as oxidation of the electroluminescent layer during a subsequent sealing step can be prevented.

A sealing member is formed, and sealing with a sealing substrate is performed. Thereafter, a flexible wiring board may be connected to a gate wiring layer which is formed to be electrically connected to the gate electrode layer 103, so that electrical connection to outside may be obtained. This can be also applied to a source wiring layer which is formed to be electrically connected to the source or drain electrode layer 116 which is also a source wiring layer.

A space between the substrate 100 provided with the element and the sealing substrate is filled with a filler and sealing therebetween is performed. A dripping method can also be used for disposing the filler. Instead of the filler, an inert gas such as nitrogen may be used for filling the space. Further, by providing a drying agent in the display device, deterioration due to moisture in the light-emitting element can be prevented. The drying agent may be provided either on the sealing substrate side or the substrate 100 side provided with the element, and may be provided by forming a concave portion in a region where the sealing member is formed in the substrate. Further, by providing the drying agent in a portion corresponding to a region which does not contribute to display, such as a driver circuit region or a wiring region of the sealing substrate, an aperture ratio is not decreased even if the drying agent is an opaque substance. The filler may contain a hygroscopic material so as to have a function as a drying agent. Through the above-described process, a display device having a display function using a light-emitting element is completed.

Although the case where a switching TFT has a single gate structure is described in this embodiment mode, the switching TFT may employ a multi-gate structure such as a double-gate structure. Further, when the semiconductor layer is formed of an SAS or a crystalline semiconductor, an impurity region can be formed by adding an impurity imparting one conductivity type. In this case, the semiconductor layer may have impurity regions with different concentrations. For example, a low-concentration impurity region may be formed around a channel region and in a region overlapping with the gate electrode layer, and a high-concentration impurity region may be formed in a region outside the low-concentration region.

This embodiment mode can be combined with any of Embodiment Modes 1 to 3 as appropriate.

By the present invention, a display device can be manufactured through a simplified process with a complicated photolithography process reduced, so that loss of materials and the cost can be reduced. Therefore, high performance and highly reliable display devices can be manufactured with a high yield.

Embodiment Mode 5

In this embodiment mode, an example of a display device in order to manufacture a display device at low cost through a highly reliable, more simplified process is described. Specifically, a light-emitting display device using a light-emitting element as a display element is described. A method for manufacturing a display device in this embodiment mode is described with reference to FIGS. 15A and 15B.

As a base film over a substrate 140 having an insulating surface, a base film 141 a is formed using a silicon nitride oxide film to a thickness of 10-200 nm (preferably, 50-150 mn), and a base film 141 b is formed using a silicon oxynitride film to a thickness of 50-200 nm (preferably, 100-150 mn) by a sputtering method, a PVD (Physical Vapor Deposition) method, a CVD (Chemical Vapor Deposition) method such as a low-pressure CVD (LPCVD) method or a plasma CVD method, or the like. Alternatively, an acrylic acid, a methacrylic acid, or a derivative thereof; a heat-resistant high molecule such as polyimide, aromatic polyamide, or polybenzimidazole; or a siloxane resin may be used. Further alternatively, a resin material such as a vinyl resin, e.g., polyvinyl alcohol or polyvinyl butyral, an epoxy rein, a phenol resin, a novolac resin, an acrylic rein, a melamine resin, or a urethane resin may be used. Further alternatively, an organic material such as benzocyclobutene, parylene, fluorinated arylene ether, or polyimide, a composition material containing water-soluble homopolymers and water-soluble copolymers, or the like may be used. Further alternatively, an oxazole resin such as photocurable polybenzoxazole may be used.

Further, a droplet discharging method, a printing method (a method by which a pattern can be formed, such as screen printing or offset printing), a coating method such as a spin coating method, a dipping method, a dispenser method, or the like can also be used. In this embodiment mode, the base films 141 a and 141 b are formed by a plasma CVD method. As the substrate 140, a glass substrate, a quartz substrate, a silicon substrate, a metal substrate, or a stainless steel substrate having an insulating film formed on its surface may be used. Further, a plastic substrate having heat resistance enough to withstand the processing temperature in this embodiment mode, or a flexible substrate such as a film may also be used. As a plastic substrate, a substrate made of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), or PES (polyethersulfone) can be used. As a flexible substrate, a synthetic resin such as acrylic can be used. Since a display device manufactured in this embodiment mode has a structure in which light is extracted from a light-emitting element through the substrate 140, it is necessary that the substrate 140 has a light-transmitting property.

As the base film, silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, or the like can be used, and either a single-layer structure or a stacked-layer structure such as a structure including two or three layers may be employed.

Next, a semiconductor film is formed over the base films. The semiconductor film may be formed to a thickness of 25-200 nm (preferably, 30-150 mn) by various methods (e.g., a sputtering method, an LPCVD method, or a plasma CVD method). In this embodiment mode, it is preferable to use a crystalline semiconductor film which is obtained by crystallizing an amorphous semiconductor film by laser.

The semiconductor film thus obtained may be doped with a slight amount of an impurity element (boron or phosphorus) in order to control a threshold voltage of a thin film transistor. Such doping with the impurity element may be performed on the amorphous semiconductor film prior to the crystallization step. If the amorphous semiconductor film is doped with the impurity element, activation of the impurities can also be performed by subsequent heat treatment for crystallization. Furthermore, a defect or the like caused in doping can be recovered.

Next, the crystalline semiconductor film is processed into a desired shape by etching, thereby forming a semiconductor layer.

Although either plasma etching (dry etching) or wet etching may be employed for the etching, plasma etching is suitable to process a large substrate. As an etching gas, a fluorine-based gas such as CF₄ or NF₃ or a chlorine-based gas such as Cl₂ or BCl₃ is used. An inert gas such as He or Ar may be added as needed. Further, by employing an etching process using atmospheric discharge plasma, a local discharge process can also be performed, so that a mask layer does not need to be formed over an entire surface of a substrate.

In the present invention, a conductive layer forming a wiring layer or an electrode layer, a mask layer for forming a predetermined pattern, or the like may be formed by a method by which a pattern can be selectively formed, such as a droplet discharging method. By a droplet discharging (jetting) method (also called an ink-jet method depending on its system), droplets of a composition which is mixed for a particular purpose are selectively discharged (jetted) to form a predetermined pattern (e.g., a conductive layer or an insulating layer). At this time, treatment to control wettablity or adhesion may be performed on a formation region. Further, a method by which a pattern can be printed (transposed) or drawn, such as a printing method (a method for forming a pattern, such as screen printing or offset printing), or a dispenser method may also be used.

A gate insulating layer covering the semiconductor layer is formed. The gate insulating layer is formed of an insulating film containing silicon to a thickness of 10-150 nm by a plasma CVD method, a sputtering method, or the like. The gate insulating layer may be formed of a material such as an oxide material or a nitride material of silicon, typified by silicon nitride, silicon oxide, silicon oxynitride, or silicon nitride oxide, and may be a stacked layer or a single layer. For example, the insulating layer may have a stacked-layer structure of three layers including a silicon nitride film, a silicon oxide film, and a silicon nitride film, or a single-layer structure of a silicon oxynitride film or a stacked-layer structure of two layers thereof.

Next, a gate electrode layer is formed over the gate insulating layer. The gate electrode layer can be formed by a sputtering method, an evaporation method, a CVD method, or the like. The gate electrode layer may be formed of an element selected from tantalum (Ta), tungsten (W), titanium (Ti), molybdenum (Mo), aluminum (Al), copper (Cu), chromium (Cr), and neodymium (Nd), or an alloy material or a compound material containing the above element as its main component. Further, as the gate electrode layer, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus, or an alloy containing silver, lead, and copper may also be used. The gate electrode layer may be either a single layer or a stacked layer.

Although the gate electrode layer is formed into a tapered shape in this embodiment mode, the present invention is not limited thereto. The gate electrode layer may employ a stacked layer structure, where only one layer has a tapered shape while the other has a perpendicular side surface by anisotropic etching. The taper angles may be different between the stacked gate electrode layers as in this embodiment mode or may be the same. With the tapered shape, coverage with a film stacked thereover is improved and a defect is reduced, so that reliability is improved.

The gate insulating layer may be etched to some extent so that reduction in thickness (so-called film reduction) may be caused by the etching step for forming the gate electrode layer.

An impurity element is added to the semiconductor layer to form an impurity region. The impurity region can be formed as a high-concentration impurity region or a low-concentration impurity region by controlling the concentration of the impurity element. A thin film transistor having a low-concentration impurity region is referred to as a thin film transistor having an LDD (Lightly Doped Drain) structure. Further, the low-concentration impurity region can be formed so as to overlap a gate electrode; such a thin film transistor is referred to as a thin film transistor having a GOLD (Gate Overlapped LDD) structure. The conductivity type of the thin film transistor is set to n type by adding phosphorus (P) or the like in the impurity region thereof. In the case where a p-channel thin film transistor is formed, boron (B) or the like may be added.

In this embodiment mode, a region of the impurity region, which overlaps the gate electrode layer with the gate insulating layer interposed therebetween, is referred to as an Lov region. Further, the other region of the impurity region, which does not overlap the gate electrode layer with the gate insulating layer interposed therebetween, is referred to as an Loff region. In FIG. 15B, the impurity regions are shown by hatching and a blank. This does not mean that the region shown by the blank is not doped with the impurity element, but makes it easy to understand that the concentration distribution of the impurity element in this impurity region reflects the mask and the doping condition. Note that this can be applied to the other drawings of this specification.

In order to activate the impurity element, heat treatment, intense light irradiation, or laser beam irradiation may be performed. At the same time as the activation, plasma damage to the gate insulating layer and plasma damage to the interface between the gate insulating layer and the semiconductor layer can be recovered.

Next, a first interlayer insulating layer covering the gate electrode layer and the gate insulating layer is formed. In this embodiment mode, a stacked-layer structure of insulating films 167 and 168 is used. As each of the insulating films 167 and 168, a silicon nitride film, a silicon nitride oxide film, a silicon oxynitride film, a silicon oxide film, or the like can be formed by a sputtering method or a plasma CVD method. Further, a single layer of another insulating film containing silicon or a stacked-layer structure including three or more layers thereof may also be used.

Further, heat treatment is performed at 300-550° C. for 1 to 12 hours in a nitrogen atmosphere, thereby hydrogenating the semiconductor layer. Preferably, the heat treatment is performed at 400-500° C. In this step, dangling bonds in the semiconductor layer are terminated by hydrogen contained in the insulating film 167 which is an interlayer insulating layer. In this embodiment mode, heat treatment is performed at 410° C.

Each of the insulating films 167 and 168 may also be formed of a material selected from aluminum nitride, aluminum oxynitride, aluminum nitride oxide containing more nitrogen than oxygen, aluminum oxide, diamond-like carbon (DLC), nitrogen-containing carbon, polysilazane, and other substances containing an inorganic insulating material. A material containing siloxane may also be used. Alternatively, an organic insulating material such as polyimide, acrylic, polyamide, polyimide amide, resist, or benzocyclobutene may be used. Further alternatively, an oxazole resin can be used, and for example, photocurable polybenzoxazole or the like can be used.

Next, a contact hole (an opening) which reaches the semiconductor layer is formed in the insulating films 167 and 168, and the gate insulating layer.

In this embodiment mode, the opening is formed by laser light as described in Embodiment Mode 1. A source region and a drain region of the semiconductor layer are selectively irradiated with laser light from the insulating films 167 and 168 side, and the insulating films 167 and 168 and the gate insulating layer over irradiated regions of the source region and the drain region of the semiconductor layer are removed by the irradiated energy, so that openings can be formed. A shape of the opening can be controlled by an irradiated region (spot) of laser light and a shape of the source or drain electrode layer to which laser light irradiation is performed.

A source electrode layer and a drain electrode layer are formed in the openings where the source region and the drain region of the semiconductor layer are exposed, thereby the source region and the drain region of the semiconductor layer can be electrically connected to the source electrode layer and the drain electrode layer.

Each of the source electrode layer and the drain electrode layer can be formed as follows; a conductive film is formed by a PVD method, a CVD method, an evaporation method, or the like, and is processed into a desired shape. Alternatively, a conductive layer can be selectively formed in a predetermined portion by a droplet discharging method, a printing method, a dispenser method, an electrolytic plating method, or the like. Further alternatively, a reflow method or a damascene method may be used. As a material of each of the source electrode layer and the drain electrode layer, a metal such as Ag, Au, Cu, Ni, Pt, Pd, Ir, Rh, W, Al, Ta, Mo, Cd, Zn, Fe, Ti, Si, Ge, Zr, or Ba, or an alloy or metal nitride thereof is used. Further, a stacked-layer structure thereof may also be employed.

Each of the gate electrode layer, the semiconductor layer, the source electrode layer, and the drain electrode layer included in the display device of this embodiment mode can also be formed as follows, as described in Embodiment Mode 3: a light-absorbing film using a conductive material or a semiconductor material is formed over a transposing substrate, and irradiated with laser light, so as to be formed selectively over a transposed substrate while being processed into a desired shape. Accordingly, the manufacturing process is simplified because a photolithography process is not used, so that loss of materials and the cost can be reduced.

Through the above-described steps, an active matrix substrate can be manufactured, in which a p-channel thin film transistor 285 having a p-type impurity region in an Lov region and an n-channel thin film transistor 275 having an n-type impurity region in an Lov region are provided in a peripheral driver circuit region 204; and a multi-channel type n-channel thin film transistor 265 having an n-type impurity region in an Loff region and a p-channel thin film transistor 255 having a p-type impurity region in an Lov region are provided in a pixel region 206.

The present invention is not limited to this embodiment mode, and the structure of each thin film transistor may be a single gate structure in which one channel formation region is formed, a double-gate structure in which two channel formation regions are formed, or a triple-gate structure in which three channel formation regions are formed.

Next, an insulating film 181 is formed as a second interlayer insulating layer. In FIGS. 15A and 15B, a separation region 201 for separation by scribing, an external terminal connection region 202 to which an FPC is attached, a wiring region 203 which is a lead wiring region for the peripheral portion, the peripheral driver circuit region 204, and the pixel region 206 are provided. Wirings 179 a and 179 b are provided in the wiring region 203, and a terminal electrode layer 178 connected to an external terminal is provided in the external terminal connection region 202.

The insulating film 181 can be formed of a material selected from silicon oxide, silicone nitride, silicon oxynitride, silicon nitride oxide, aluminum nitride, aluminum oxide containing nitrogen (also called aluminum oxynitride), aluminum nitride oxide containing oxygen (also called aluminum nitride oxide), aluminum oxide, diamond-like carbon (DLC), nitrogen-containing carbon, PSG (phosphosilicate glass), BPSG (borophosphosilicate glass), alumina, and other substances containing an inorganic insulating material. Further, a siloxane resin may also be used. Further alternatively, an organic insulating material which is either photosensitive or non-photosensitive, such as polyimide, acrylic, polyamide, polyimide amide, resist, benzocyclobutene, or a low-dielectric constant material (Low-k material) may be used. Further alternatively, an oxazole resin can be used, and for example, photocurable polybenzoxazole or the like may be used. It is necessary that an interlayer insulating layer provided for planarization has high heat resistance, a high insulating property, and high planarity; therefore, a coating method typified by a spin coating method is preferably employed for forming the insulating film 181.

The insulating film 181 can be formed by a dipping method, spray coating, a doctor knife, a roll coater, a curtain coater, a knife coater, a CVD method, an evaporation method, or the like. Further, the insulating film 181 may also be formed by a droplet discharging method. In the case of employing a droplet discharging method, a material solution can be saved. Alternatively, a method by which a pattern can be printed or drawn, like a droplet discharging method, such as a printing method (a method for forming a pattern, such as screen printing or offset printing), a dispenser method, or the like may be employed.

A minute opening, that is, a contact hole is formed in the insulating film 181 in the pixel region 206. The source or drain electrode layer is electrically connected to a first electrode layer 185 in the opening formed in the insulating film 181. The opening formed in the insulating film 181 can be formed as described in Embodiment Mode 1, by laser light irradiation. A shape of the opening can be controlled by an irradiated region (spot) of laser light and a shape of the source or drain electrode layer to which laser light irradiation is performed.

In this embodiment mode, a low-melting point metal (chromium in this embodiment mode) that is relatively easily evaporated is used for the source or drain electrode layer. The source or drain electrode layer is selectively irradiated with laser light from the gate insulating film 181 side, and the insulating film 181 above an irradiated region of the source or drain electrode layer is removed by irradiated energy, so that the opening can be formed. The first electrode layer 185 is formed in the opening where the source or drain electrode layer is exposed, thereby electrically connected to the source or drain electrode layer.

The first electrode layer 185 functions as either an anode or a cathode, as which a film containing an element selected from titanium, nickel, tungsten, chromium, platinum, zinc, tin, indium, and molybdenum, or an alloy material or a compound material containing the above element as its main component, such as titanium nitride, titanium silicon nitride, tungsten silicide, tungsten nitride, tungsten silicon nitride, or niobium nitride, or a stacked-layer film thereof with a total thickness of 10-800 nm may be used.

In this embodiment mode, since a light-emitting element is used as a display element, and light from the light-emitting element is extracted from the first electrode layer 185 side, the first electrode layer 185 has a light-transmitting property. The first electrode layer 185 is formed by forming a transparent conductive film and etching into a desired shape.

In the present invention, as the first electrode layer 185 which is a light-transmitting electrode layer, a transparent conductive film formed of a light-transmitting conductive material may be used specifically, and for example, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, or the like can be used. It is needless to say that indium tin oxide (ITO), indium zinc oxide (IZO), indium tin oxide added with silicon oxide (ITSO), or the like can also be used.

Further, even in the case of a material which does not have a light-transmitting property, such as a metal film, when the thickness is small (preferably, about 5-30 nm) so that light can be transmitted, light can be emitted through the first electrode layer 185. As the metal thin film which can be used as the first electrode layer 185, a conductive film formed of titanium, tungsten, nickel, gold, platinum, silver, aluminum, magnesium, calcium, lithium, or an alloy thereof, or the like can be used.

The first electrode layer 185 can be formed by an evaporation method, a sputtering method, a CVD method, a printing method, a dispenser method, a droplet discharging method, or the like. In this embodiment mode, the first electrode layer 185 is formed by a sputtering method using indium zinc oxide containing tungsten oxide. The first electrode layer 185 is preferably formed to a total thickness of 100-800 nm. The first electrode layer 185 may also be formed as follows, as described in Embodiment Mode 3: a conductive light-absorbing film is formed over a transposing substrate, and irradiated with laser light so as to be selectively formed over a transposed substrate while being processed into a desired shape.

The first electrode layer 185 may be cleaned and polished by a CMP method or using a polyvinyl-alcohol-based porous body so as to planarize the surface thereof. Further, after being polished using a CMP method, the surface of the first electrode layer 185 may be subjected to ultraviolet light irradiation, oxygen plasma treatment, or the like.

Heat treatment may also be performed after the first electrode layer 185 is formed. By this heat treatment, moisture contained in the first electrode layer 185 is discharged. Accordingly, degasification or the like is not caused in the first electrode layer 185; thus, even when a light-emitting material that is easily deteriorated by moisture is formed over the first electrode layer, the light-emitting material is not deteriorated, and a highly reliable display device can be manufactured.

Next, an insulating layer 186 (also called a partition wall, a barrier, or the like) covering an end portion of the first electrode layer 185 and the source or drain electrode layer is formed.

The insulating layer 186 may be formed of silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, or the like and employ a single-layer structure or a stacked-layer structure such as a structure including two or three layers. Further, the insulating layer 186 may also be formed of a material selected from aluminum nitride, aluminum oxynitride containing more oxygen than nitrogen, aluminum nitride oxide containing more nitrogen than oxygen, diamond-like carbon (DLC), nitrogen-containing carbon, polysilazane, and other substances containing an inorganic insulating material. A material containing siloxane may also be used. Alternatively, an organic insulating material which is either photosensitive or non-photosensitive, such as polyimide, acrylic, polyamide, polyimide amide, resist, benzocyclobutene, or polysilazane may be used. Further alternatively, an oxazole resin can be used, and for example, photocurable polybenzoxazole or the like can be used.

The insulating layer 186 can be formed by a sputtering method, a PVD (Physical Vapor Deposition) method, a CVD (Chemical Vapor Deposition) method such as a low-pressure CVD (LPCVD) method or a plasma CVD method, or the like. Further, a droplet discharging method, various printing methods (a method for forming a pattern, such as screen printing or offset printing), a coating method such as a spin-coating method, a dipping method, a dispenser method, or the like may also be used.

Although either plasma etching (dry etching) or wet etching may be employed for the etching to process into the desired shape, plasma etching is suitable to process a large substrate. As an etching gas, a fluorine-based gas such as CF₄ or NF₃ or a chlorine-based gas such as Cl₂ or BCl₃ is used. An inert gas such as He or Ar may be added as needed. Further, by employing an etching process using atmospheric discharge plasma, a local discharging process can also be performed, and the mask layer does not need to be formed over the entire surface of the substrate.

In a connection region 205 shown in FIG. 15A, a wiring layer formed of the same material and by the same step as a second electrode layer is electrically connected to a wiring layer formed of the same material and by the same step as the gate electrode layer.

A light-emitting layer 188 is formed over the first electrode layer 185. Although only one pixel is shown in FIGS. 15A and 15B, respective electric field electrode layers corresponding to R (red), G (green), and B (blue) are formed separately in this embodiment mode.

Next, a second electrode layer 189 formed of a conductive film is provided over the light-emitting layer 188. As the second electrode layer 189, Al, Ag, Li, Ca, or an alloy or a compound thereof such as MgAg, MgIn, AlLi, or CaF₂, or calcium nitride may be used. In this manner, a light-emitting element 190 including the first electrode layer 185, the light-emitting layer 188, and the second electrode layer 189 is formed (see FIG. 15B).

In the display device of this embodiment mode shown in FIGS. 15A and 15B, light from the light-emitting element 190 is transmitted through the first electrode layer 185 in a direction denoted by an arrow in FIG. 15B.

In this embodiment mode, an insulating layer may be provided as a passivation film (a protective film) over the second electrode layer 189. It is effective to thus provide the passivation film so as to cover the second electrode layer 189. The passivation film is formed of an insulating film containing silicon nitride, silicon oxide, silicon oxynitride, silicon nitride oxide, aluminum nitride, aluminum oxynitride, aluminum nitride oxide containing more nitrogen than oxygen, aluminum oxide, diamond-like carbon (DLC), or nitrogen-containing carbon, and can employ a single-layer structure of the insulating film or a stacked-layer structure thereof. Alternatively, a siloxane resin may be used.

In this case, it is preferable to use, as the passivation film, a film with which favorable coverage is provided, and it is effective to use a carbon film, particularly a DLC film. A DLC film, which can be formed in the range from room temperature to equal to or less than 100° C., can also be formed easily over the light-emitting layer 188 with low heat resistance. A DLC film can be formed by a plasma CVD method (typically, an RF plasma CVD method, a microwave CVD method, an electron cyclotron resonance (ECR) CVD method, a thermal-filament CVD method, or the like), a combustion flame method, a sputtering method, an ion beam evaporation method, a laser evaporation method, or the like. As a reaction gas for deposition, a hydrogen gas and a hydrocarbon-based gas (e.g., CH₄, C₂H₂, C₆H₆, or the like) are used to be ionized by glow discharge, and the ions are accelerated to impact against a cathode to which negative self bias is applied. Further, a CN film may be formed using a C₂H₄ gas and a N₂ gas as reaction gases. A DLC film has a high blocking effect against oxygen; therefore, oxidization of the light-emitting layer 188 can be suppressed. Accordingly, a problem such as oxidation of the light-emitting layer 188 during a subsequent sealing step can be prevented.

The substrate 140 over which the light-emitting element 190 is thus formed and a sealing substrate 195 are firmly attached to each other by using a sealing member 192, so that the light-emitting element is sealed (see FIGS. 15A and 15B). As the sealing member 192, typically, a visible light curable resin, an ultraviolet curable resin, or a thermosetting resin is preferably used. For example, the following one can be used: a bisphenol-A liquid resin, a bisphenol-A solid resin, a bromine-containing epoxy resin, a bisphenol-F resin, a bisphenol-AD resin, a phenol resin, a cresol resin, a novolac resin, a cycloaliphatic epoxy resin, an Epi-Bis epoxy resin, a glycidyl ester resin, a glycidyl amine-based resin, a heterocyclic epoxy resin, a modified epoxy resin, or the like. Note that a region surrounded by the sealing member may be filled with a filler 193, and may be filled with nitrogen or the like by performing sealing in a nitrogen atmosphere. Although the filler 193 does not necessarily have a light-transmitting property in this embodiment mode because of a bottom emission type, it is necessary that the filler has a light-transmitting property in the case where light is extracted through the filler 193. Typically, a visible light curable epoxy resin, an ultraviolet curable epoxy resin, or a thermosetting epoxy resin may be used. Through the above-described steps, a display device having a display function using a light-emitting element of this embodiment mode is completed. Further, the filler may be dropped in a liquid state to fill the display device. In the case of using a hygroscopic substance such as a drying agent as the filler, a further moisture absorption effect can be obtained, thereby preventing deterioration of the element.

A drying agent is provided in an EL display panel in order to prevent deterioration due to moisture in the element. In this embodiment mode, the drying agent is provided in a concave portion which is formed in the sealing substrate so as to surround the pixel region, thereby the thin design is not hindered. Further, when the drying agent is also provided in a region corresponding to a gate wiring layer so that a moisture absorbing area is increased, the moisture absorption effect becomes high. Further, when the drying agent is provided over the gate wiring layer which does not emit light itself, the light extraction efficiency is not decreased.

The light-emitting element is sealed by a glass substrate in this embodiment mode. Note that sealing treatment is a treatment for protecting a light-emitting element from moisture, and any of the following methods is used: a method for mechanically sealing by a cover member, a method for sealing with a thermosetting resin or an ultraviolet light curable resin, and a method for sealing by a thin film having a high barrier property such as a metal oxide film or a metal nitride film. As the cover member, glass, ceramics, plastics, or metal can be used, and it is necessary that the cover member has a light-transmitting property in the case where light is emitted to the cover member side. Further, the cover member and the substrate over which the light-emitting element is formed are attached to each other with a sealing member such as a thermosetting resin or an ultraviolet curable resin, and the resin is cured by heat treatment or ultraviolet light irradiation treatment to form a sealed space. It is also effective to provide a moisture absorbent typified by barium oxide in this sealed space. This moisture absorbent may be provided on and in contact with the sealing member, or over or in the periphery of the partition wall so as not to shield light from the light-emitting element. Further, the space between the cover member and the substrate over which the light-emitting element is formed can be filled with a thermosetting resin or an ultraviolet light curable resin. In this case, it is effective to add a moisture absorbent typified by barium oxide in the thermosetting resin or the ultraviolet light curable resin.

Further, the source or drain electrode layer and the first electrode layer are not necessarily in direct contact with each other to be electrically connected, but may be connected to each other through a wiring layer.

In this embodiment mode, the terminal electrode layer 178 is connected to an FPC 194 through an anisotropic conductive layer 196 in the external terminal connection region 202, thereby electrically connecting to outside. Further, as shown in FIG. 15A which is a top diagram of the display device, the display device manufactured in this embodiment mode includes peripheral driver circuit regions 204 and 209 each including a signal line driver circuit in addition to a peripheral driver circuit region 207 and a peripheral driver circuit region 208 each including a scan line driver circuit.

Although the above-described circuits are included in this embodiment mode, the present invention is not limited thereto. An IC chip may be mounted by the aforementioned COG method or TAB method as a peripheral driver circuit. Further, the number of each of gate line driver circuits and source line driver circuits is not particularly limited.

Further, in the display device of the present invention, a driving method for image display is not particularly limited; for example, a dot sequential driving method, a line sequential driving method, a frame sequential driving method, or the like may be used. Typically, a line sequential driving method may be used, and a time division gray scale driving method or an area gray scale driving method may be used as appropriate. Further, a video signal to be inputted to a source line of the display device may be either an analog signal or a digital signal; and in accordance with the video signal, the driver circuit and the like may be appropriately designed.

This embodiment mode can be combined with any of Embodiment Modes 1 to 3 as appropriate.

By the present invention, a display device can be manufactured through a simplified process with a complicated photolithography process reduced, so that loss of materials and the cost can be reduced. Therefore, high performance and highly reliable display devices can be manufactured with a high yield.

Embodiment Mode 6

A thin film transistor can be formed by the present invention, and a display device can be formed using the thin film transistor. In the case where a light-emitting element is used and an n-channel transistor is used as a transistor for driving the light-emitting element, light emission from the light-emitting element is one of bottom emission, top emission, and dual emission. Here, respective stacked-layer structures of the light-emitting element in the cases are described with reference to FIGS. 17A to 17C.

In this embodiment mode, channel protective thin film transistors 461, 471, and 481 to which the present invention is applied are used. The thin film transistor 481 is provided over a light-transmitting substrate 480 and includes a gate electrode layer 493, a gate insulating layer 497, a semiconductor layer 494, an n-type semiconductor layer 495 a, an n-type semiconductor layer 495 b, a source or drain electrode layer 487 a, a source or drain electrode layer 487 b, a channel protective layer 496, an insulating layer 499, and a wiring layer 498. Any of the gate electrode layer, the semiconductor layer, the source electrode layer, the drain electrode layer, and the like may also be formed as follows, as described in Embodiment Mode 3: a conductive light-absorbing film is formed over a transposing substrate, and irradiated with laser light, so as to be formed selectively over a transposed substrate while being processed into a desired shape. Accordingly, the manufacturing process is simplified, so that loss of materials and the cost can be reduced.

In FIGS. 17A to 17C described in this embodiment mode, a contact hole (an opening) which reaches the source or drain electrode layer 487 b is formed in the insulating layer 499.

In this embodiment mode, the opening is formed by laser light as described in Embodiment Mode 1. The source or drain electrode layer 487 b is selectively irradiated with laser light from the insulating layer 499 side, and the insulating layer 499 above an irradiated region of the source or drain electrode layer 487 b can be removed by the irradiation energy, so that the opening can be formed.

The wiring layer 498 is formed in the opening where the source or drain electrode layer 487 b is exposed, thereby the source or drain electrode layer 487 b can be electrically connected to the wiring layer 498. Since the wiring layer 498 is connected to a first electrode layer 484 of a light-emitting element, the thin film transistor 481 and the light-emitting element are electrically connected to each other through the wiring layer 498.

In this embodiment mode, an amorphous semiconductor layer is used as the semiconductor layer. However, the present invention is not limited to this embodiment mode; a crystalline semiconductor layer can also be used as the semiconductor layer, and an n-type semiconductor layer can also be used as the semiconductor layer having one conductivity type. Instead of forming the n-type semiconductor layer, conductivity type may be provided for a semiconductor layer by plasma treatment using a PH₃ gas. In the case where a crystalline semiconductor layer of polysilicon or the like is used, an impurity region having one conductivity type may be formed by introducing (adding) an impurity into the crystalline semiconductor layer without forming a semiconductor layer having one conductivity type. Further, an organic semiconductor such as pentacene may also be used. By selectively depositing the organic semiconductor with a droplet discharging method or the like, the processing process can be simplified.

The case where a crystalline semiconductor layer is used as the semiconductor layer is described. First, an amorphous semiconductor layer is crystallized to form a crystalline semiconductor layer. In a crystallization step, an element which promotes crystallization (also referred to as a catalytic element or a metal element) is added into the amorphous semiconductor layer, and crystallization is performed by heat treatment (at 550-750° C. for 3 minutes to 24 hours). As the metal element which promotes crystallization of silicon, one or a plurality of kinds of elements selected from iron (Fe), nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), copper (Cu), and gold (Au) can be used.

In order to remove or reduce the element which promotes crystallization from the crystalline semiconductor layer, a semiconductor layer containing an impurity element is formed to be in contact with the crystalline semiconductor layer and is made to function as a gettering sink. As the impurity element, an impurity element imparting n-type conductivity, an impurity element imparting p-type conductivity, a rare gas element, or the like can be used. For example, one or a plurality of kinds of elements selected from phosphorus (P), nitrogen (N), arsenic (As), antimony (Sb), bismuth (Bi), boron (B), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) can be used. An n-type semiconductor layer is formed to be in contact with the crystalline semiconductor layer containing the element which promotes crystallization, and heat treatment (at 550-750° C. for 3 minutes to 24 hours) is performed. The element which promotes crystallization contained in the crystalline semiconductor layer moves into the n-type semiconductor layer, and the element which promotes crystallization contained in the crystalline semiconductor layer is removed or reduced, so that the semiconductor layer is formed. On the other hand, the n-type semiconductor layer becomes an n-type semiconductor layer containing the metal element which promotes crystallization, and then processed into a desired shape to be an n-type semiconductor layer. In this manner, the n-type semiconductor layer functions as a gettering sink of the semiconductor layer, and also as a source region or a drain region as it is.

The crystallization step and the gettering step of the semiconductor layer may also be performed by either a plurality of heat treatment or one heat treatment. In the latter case, heat treatment may be performed after the following: an amorphous semiconductor layer is formed, an element which promotes crystallization is added, and a semiconductor layer which functions as a gettering sink is formed.

In this embodiment mode, the gate insulating layer is formed by stacking a plurality of layers, and a silicon nitride oxide film and a silicon oxynitride film are stacked on the gate electrode layer 493 side, as the gate insulating film 497 employing a two-layer structure. The insulating layers stacked are preferably formed successively at the same temperature in the same chamber while changing a reaction gas without breaking a vacuum. By forming the layers successively without breaking a vacuum, an interface between the stacked layers can be prevented from being contaminated.

The channel protective layer 496 may be formed by a droplet discharging method using polyimide, polyvinyl alcohol, or the like. As a result, a light exposure step can be omitted. The channel protective layer can be formed using one or a plurality of kinds of the following or a stacked layer thereof: an inorganic material (e.g., silicon oxide, silicon nitride, silicon oxynitride, or silicon nitride oxide), a photosensitive or non-photosensitive organic material (an organic resin material) (e.g., polyimide, acrylic, polyamide, polyimide amide, resist, or benzocyclobutene), a low-dielectric constant material, and the like. Further, a siloxane material may also be used. As a method for manufacturing the channel protective layer 496, a vapor deposition method such as a plasma CVD method or a thermal CVD method, or a sputtering method can be used. Alternatively, a droplet discharging method, a dispenser method, or a printing method (a method for forming a pattern, such as screen printing or offset printing) may be used. An SOG film obtained by a coating method, or the like may be used as well.

First, the case where light is emitted to the substrate 480 side, that is, the case of bottom emission is described with reference to FIG. 17A. In this case, the wiring layer 498, the first electrode layer 484, an electroluminescent layer 485, and a second electrode layer 486 are stacked sequentially so as to be in contact with the source or drain electrode layer 487 b, thereby electrically connecting to the thin film transistor 481. It is necessary that the substrate 480 through which light is transmitted has a light-transmitting property against at least visible light.

Next, the case where light is emitted to the side opposite to a substrate 460, that is, the case of top emission is described with reference to FIG. 17B. The thin film transistor 461 can be formed similarly to the thin film transistor 481 described above. A source or drain electrode layer 462 electrically connected to the thin film transistor 461 is in contact with a first electrode layer 463 so that they are electrically connected to each other. The first electrode layer 463, an electroluminescent layer 464, and a second electrode layer 465 are sequentially stacked. The source or drain electrode layer 462 is a metal layer having light reflectivity and reflects light which is emitted from the light-emitting element, upward as shown by an arrow. Since the source or drain electrode layer 462 is stacked over the first electrode layer 463, even when the first electrode layer 463 is formed of a light-transmitting material and transmits light, the light is reflected on the source or drain electrode layer 462 and then is emitted to the direction opposite to the substrate 460. It is needless to say that the first electrode layer 463 may also be formed of a metal film having light reflectivity. Light from the light-emitting element is transmitted through the second electrode layer 465; therefore, the second electrode layer 465 is formed of a material having a light-transmitting property against at least visible light.

Finally, the case where light is emitted to the substrate 470 side and to the side opposite to the substrate 470 side, that is, the case of dual emission is described with reference to FIG. 17C. The thin film transistor 471 is also a channel protective thin film transistor. A source or drain electrode layer electrically connected to a semiconductor layer of the thin film transistor 471 is electrically connected to a wiring layer 475 and a first electrode layer 472. The first electrode layer 472, an electroluminescent layer 473, and a second electrode layer 474 are sequentially stacked. At this time, by using materials having a light-transmitting property against at least visible light as both of the first electrode layer 472 and the second electrode layer 474 or forming both of them to have thicknesses enough to transmit light, dual emission is realized. In this case, it is necessary that the insulating layer and the substrate 470 through which light is transmitted have a light-transmitting property against at least visible light.

This embodiment mode can be combined with any of Embodiment Modes 1 to 5 as appropriate.

By the present invention, components such as a wiring included in a display device can be formed to have a desired shape. Further, a display device can be manufactured through a simplified process with a complicated photolithography process reduced, so that loss of materials and the cost can be reduced. Therefore, high performance and highly reliable display devices can be manufactured with a high yield.

Embodiment Mode 7

In this embodiment mode, an example of a display device in order to manufacture a display device at low cost through a highly reliable, more simplified process is described. Specifically, a light-emitting display device using a light-emitting element as a display element is described.

In this embodiment mode, structures of the light-emitting element which can be used as the display element of the display device of the present invention are described with reference to FIGS. 22A to 22D.

FIGS. 22A to 22D each show an element structure of a light-emitting element where an electroluminescent layer 860 formed of a mixture of an organic compound and an inorganic compound is interposed between a first electrode layer 870 and a second electrode layer 850. As shown in the drawings, the electroluminescent layer 860 includes a first layer 804, a second layer 803, and a third layer 802.

First, the first layer 804 is a layer which has a function of transporting holes to the second layer 803, and includes at least a first organic compound and a first inorganic compound having an electron-accepting property with respect to the first organic compound. It is important that the first organic compound and the first inorganic compound are not simply mixed but the first inorganic compound has an electron-accepting property with respect to the first organic compound. With this structure, many hole-carriers are generated in the first organic compound which has originally almost no inherent carriers, and highly excellent hole-injecting property and hole-transporting property can be provided.

Accordingly, the first layer 804 can be provided with not only an advantageous effect that is considered to be obtained by mixing an inorganic compound (e.g., improvement in heat resistance) but also with excellent conductivity (in particular, a hole-injecting property and a hole-transporting property in the first layer 804). This is an advantageous effect, which cannot be obtained in a conventional hole-transporting layer in which an organic compound and an inorganic compound that do not electronically interact with each other are simply mixed. This advantageous effect can make a driving voltage lower than the conventional one. Further, since the first layer 804 can be thickened without causing a rise in driving voltage, a short circuit of the element due to dust or the like can be suppressed.

As described above, hole carriers are generated in the first organic compound; therefore, a hole-transporting organic compound is preferably used as the first organic compound. As examples of the hole-transporting organic compound, the following can be given: phthalocyanine (abbreviation: H₂Pc), copper phthalocyanine (abbreviation: CuPc), vanadyl phthalocyanine (abbreviation: VOPc), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 1,3,5-tris[N,N-di(m-tolyl)amino]benzene (abbreviation: m-MTDAB), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (abbreviation: TPD), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), 4,4′-bis{N-[4-di(m-tolyl)amino]phenyl-N-phenylamino}biphenyl (abbreviation: DNTPD), 4,4′,4″-tris(N-carbazolyl)triphenylamine (abbreviation: TCTA), and the like. The present invention is not limited thereto. In addition, among the compounds described above, an aromatic amine compound such as TDATA, MTDATA, m-MTDAB, TPD, NPB, DNTPD, TCTA, or the like can easily generate hole carriers and is a suitable compound group for the first organic compound.

On the other hand, the first inorganic compound may be any material as long as electrons can be easily accepted from the first organic compound, and various metal oxides and metal nitrides can be used. Any of transition metal oxides that belong to Groups 4 to 12 of the periodic table is preferable because an electron-accepting property is easily exhibited. Specifically, titanium oxide, zirconium oxide, vanadium oxide, molybdenum oxide, tungsten oxide, rhenium oxide, ruthenium oxide, zinc oxide, and the like can be given as examples thereof. Among the metal oxides described above, transition metal oxides that belong to Groups 4 to 8 of the periodic table mostly have a high electron-accepting property, which is a preferable group. In particular, vanadium oxide, molybdenum oxide, tungsten oxide, and rhenium oxide are preferable because they can be deposited by vacuum evaporation and can be easily handled.

Note that the first layer 804 may also be formed by stacking a plurality of layers each containing the mixture of the organic compound and the inorganic compound described above, and may further contain another organic compound or inorganic compound.

Next, the third layer 802 is described. The third layer 802 is a layer having a function of transporting electrons to the second layer 803, and includes at least a third organic compound and a third inorganic compound having an electron-donating property with respect to the third organic compound. It is important that the third organic compound and the third inorganic compound are not simply mixed but the third inorganic compound has an electron-denoting property with respect to the third organic compound. With this structure, many electron carriers are generated in the third organic compound which has originally almost no inherent carriers, and highly excellent electron-injecting property and electron-transporting property can be provided.

Accordingly, the third layer 802 can be provided with not only an advantageous effect that is considered to be obtained by mixing an inorganic compound (e.g., improvement in heat resistance) but also with excellent conductivity (in particular, a hole-injecting property and a hole-transporting property in the third layer 802). This is an advantageous effect, which cannot be obtained in a conventional hole-transporting layer in which an organic compound and an inorganic compound that do not electronically interact with each other are simply mixed. This advantageous effect can make a driving voltage lower than the conventional one. Further, since the third layer 802 can be thickened without causing a rise in driving voltage, a short circuit of the element due to dust or the like can be suppressed.

As described above, electron carriers are generated in the third organic compound; therefore, an electron-transporting organic compound is preferably used as the third organic compound. As examples of the electron-transporting organic compound, the following can be given: tris(8-quinolinolato)aluminum (abbreviation: Alq₃), tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃), bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: BeBq₂), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation: BAlq), bis[2-(2′-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)₂), bis [2-(2′-hydroxyphenyl)benzothiazolato]zinc (abbreviation: Zn(BTZ)₂), bathophenanthroline (abbreviation: BPhen), bathocuproin (abbreviation: BCP), 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 3-(4-biphenylyl)-4-(4-ethylphenyl)-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: p-EtTAZ), and the like. The present invention is not limited thereto. Further, among the compounds mentioned above, chelate metal complexes each having a chelate ligand including an aromatic ring such as Alq₃, Almq₃, BeBq₂, BAlq, Zn(BOX)₂, and Zn(BTZ)₂, organic compounds having a phenanthroline skeleton such as BPhen and BCP, and organic compounds having an oxadiazole skeleton such as PBD and OXD-7 can easily generate electron carriers and is a suitable compound group for the third organic compound.

On the other hand, the third inorganic compound may be any material as long as electrons can be easily denoted to the third organic compound, and various metal oxides and metal nitrides can be used. Alkali metal oxide, alkaline-earth metal oxide, rare-earth metal oxide, alkali metal nitride, alkaline-earth metal nitride, or rare-earth metal nitride is preferable because an electron-donating property is easily exhibited. Specifically, lithium oxide, strontium oxide, barium oxide, erbium oxide, lithium nitride, magnesium nitride, calcium nitride, yttrium nitride, lanthanum nitride, and the like can be given as examples thereof. In particular, lithium oxide, barium oxide, lithium nitride, magnesium nitride, and calcium nitride are preferable because they can be deposited by vacuum evaporation and can be easily handled.

Note that the third layer 802 may also be formed by stacking a plurality of layers each containing the mixture of the organic compound and the inorganic compound described above, and may further contain another organic compound or inorganic compound.

Next, the second layer 803 is described. The second layer 803 is a layer having a function of emitting light and includes a second organic compound having a light-emitting property. Further, a second inorganic compound may also be included. The second layer 803 can be formed using any of various light-emitting organic and inorganic compounds. However, since it is considered that a current does not easily flow through the second layer 803 as compared to the first layer 804 or the third layer 802, the thickness of the second layer 803 is preferably approximately 10-100 nm.

Any light-emitting organic compound can be used as the second organic compound. The following can be given as examples thereof: 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-di(2-naphthyl)-2-tert-butylanthracene (abbreviation: t-BuDNA), 4,4′-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi), coumarin 30, coumarin 6, coumarin 545, coumarin 545T, perylene, rubrene, periflanthene, 2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP), 9,10-diphenylanthracene (abbreviation: DPA), 5,12-diphenyltetracene, 4-(dicyanomethylene)-2-methyl-[p-(dimethylamino)styryl]-4H-pyran (abbreviation: DCM1), 4-(dicyanomethylene)-2-methyl-6-[2-oulolidin-9-yl)ethenyl]-4H-pyran (abbreviation: DCM2), 4-(dicyanomethylene)-2,6-bis[p-(dimethylamino)styryl]-4H-pyran (abbreviation: BisDCM), and the like. Further, a compound capable of emitting phosphorescence can also be used, such as bis[2-(4′,6′-difluorophenyl)pyridinato-N,C²′]iridium(picolinate) (abbreviation: FIrpic), bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C²′}iridium(picolinate) (abbreviation: Ir(CF₃ppy)₂(Pic)), tris(2-phenylpyridinato-N, c²′)iridium (abbreviation: Ir(ppy)₃), bis(2-phenylpyridinato-N,C²′)iridium(acetylacetonate) (abbreviation: Ir(Ppy)₂(acac)), bis[2-(2′-thienyl)pyridinato-N,C³′]iridium(acetylacetonate) (abbreviation: Ir(thp)₂(acac)), bis(2-phenylquinolinato-N,C²′)iridium(acetylacetonate) (abbreviation: Ir(Pq)₂(acac)), bis[2-(2′-benzothienyl)pyridinato-N,C³′]iridium(acetylacetonate) (abbreviation: Ir(btp)₂(acac)), or the like.

Further, a triplet excitation light-emitting material containing a metal complex or the like may be used for the second layer 803, as well as a singlet excitation light-emitting material. For example, among respective pixels emitting light of red, green, and blue, a pixel emitting light of red whose luminance is reduced by half in a relatively short time is formed using a triplet excitation light-emitting material and the other pixels are formed using singlet excitation light-emitting materials. A triplet excitation light-emitting material has a feature in that light-emitting efficiency is favorable, so that less power is consumed to obtain the same luminance. In other words, when a triplet excitation light-emitting: material is used for a red pixel, the amount of current needs to be applied to a light-emitting element is small; thus, reliability can be improved. Further, the pixel emitting light of red and the pixel emitting light of green may be formed using triplet excitation light-emitting materials and the pixel emitting light of blue may be formed using a singlet excitation light-emitting material in order to achieve low power consumption. Low power consumption can be further achieved by forming a light-emitting element which emits light of green that has high visibility for human eyes with a triplet excitation light-emitting material.

Further, the second layer 803 may be added with another organic compound in addition to the second organic compound which emits light, described above. The organic compound that can be added is the following: 4,4′-bis(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), or the like as well as TDATA, MTDATA, m-MTDAB, TPD, NPB, DNTPD, TCTA, Alq₃, Almq₃, BeBq₂, BAlq, Zn(BOX)₂, Zn(BTZ)₂, BPhen, BCP, PBD, OXD-7, TPBI, TAZ, p-EtTAZ, DNA, t-BuDNA, and DPVBi which are mentioned above. The present invention is not limited thereto. Note that it is preferable that the organic compound, which is added in addition to the second organic compound, have larger excitation energy than the second organic compound and be added by the larger amount than the second organic compound in order to make the second organic compound emit light efficiently (which makes it possible to prevent concentration quenching of the second organic compound). Alternatively, as another function, the added organic compound may emit light along with the second organic compound (which makes it possible to emit white light or the like).

The second layer 803 may have a structure in which color display is performed by forming light-emitting layers having different emission wavelength bands for respective pixels. Typically, respective light-emitting layers corresponding to R (red), G (green), and B (blue) are formed. Also in this case, color purity can be improved and a pixel region can be prevented from having a mirror surface (reflecting) by providing a filter which transmits light of an emission wavelength range of the light on the light-emission side of the pixel. By providing a filter, a circularly polarizing plate or the like that has been considered to be required can be omitted, and the loss of light emitted from the light-emitting layer can be eliminated. Further, change in color tone, which occurs when the pixel region (a display screen) is obliquely seen, can be reduced.

Either a low-molecular organic light-emitting material or a high-molecular organic light-emitting material can be used as a material of the second layer 803. A high-molecular organic light-emitting material has higher physical strength and provides higher durability of an element than a low-molecular material. Further, since a high-molecular organic light-emitting material can be deposited by coating, an element can be relatively easily manufactured.

The emission color is determined depending on a material included in the light-emitting layer; therefore, a light-emitting element which emits desired light can be formed by selecting an appropriate material for the light-emitting layer. As examples of a high-molecular electroluminescent material which can be used for a light-emitting layer, a polyparaphenylene-vinylene-based material, a polyparaphenylene-based material, a polythiophene-based material, a polyfluorene-based material, and the like can be given.

As an example of the polyparaphenylene-vinylene-based material, a derivative of poly(paraphenylenevinylene) [PPV] such as poly(2,5-dialkoxy-1,4-phenylenevinylene) [RO-PPV], poly(2-(2′-ethyl-hexoxy)-5-methoxy-1,4-phenylenevinylene) [MEH-PPV], or poly(2-(dialkoxyphenyl)-1,4-phenylenevinylene) [ROPh-PPV] can be given. As an example of the polyparaphenylene-based material, a derivative of polyparaphenylene [PPP] such as poly(2,5-dialkoxy-1,4-phenylene) [RO-PPP] or poly(2,5-dihexoxy-1,4-phenylene) can be given. As an example of the polythiophene-based material, a derivative of polythiophene [PT] such as poly(3-alkylthiophene) [PAT], poly(3,hexylthiophen) [PHT], poly(3-cyclohexylthiophen) [PCHT], poly(3-cyclohexyl-4-methylthiophene) [PCHMT], poly(3,4-dicyclohexylthiophene) [PDCHT], poly[3-(4-octylphenyl)-thiophene] [POPT], or poly[3-(4-octylphenyl)-2,2bithiophene] [PTOPT] can be given. As an example of the polyfluorene-based material, a derivative of polyfluorene [PF] such as poly(9,9-dialkylfluorene) [PDAF] or poly(9,9-dioctylfluorene) [PDOF] can be given.

The second inorganic compound may be any inorganic compound as long as light emission of the second organic compound is not easily quenched; various metal oxides and metal nitrides can be used. In particular, a metal oxide that belongs to Group 13 or 14 of the periodic table is preferable because light emission of the second organic compound is not easily quenched, and specifically, aluminum oxide, gallium oxide, silicon oxide, or germanium oxide is preferable. The present invention is, however, not limited thereto.

Note that the second layer 803 may be formed by stacking a plurality of layers each containing the mixture of the organic compound and the inorganic compound, which are described above, and may further include another organic compound or inorganic compound. A layer structure of the light-emitting layer can be changed, and an electrode layer for injecting electrons may be provided or a light-emitting material may be dispersed unless that departs from the purpose of the present invention, instead of providing a specific electron-injecting region or light-emitting region.

A light-emitting element formed using the above-described materials emits light by being forwardly biased. Pixels of a display device which include a light-emitting element can be driven by a simple matrix method or an active matrix method. In either case, each pixel emits light by application of forward bias thereto at a specific timing, and the pixel is in a non-emitting state for a certain period. Reliability of the light-emitting element can be improved by applying reverse bias in the non-emitting time. In a light-emitting element, there are a deterioration mode in which emission intensity is decreased under a constant driving condition and a deterioration mode in which a non-light-emitting region is increased in the pixel and luminance is apparently decreased. However, progression of deterioration can be slowed down by performing alternating driving in which bias is applied forwardly and reversely; thus, reliability of a light-emitting display device can be improved. Further, either digital driving or analog driving can be used.

Therefore, a color filter (a colored layer) may be provided for a sealing substrate. The color filter (colored layer) can be formed by an evaporation method or a droplet discharging method. High-definition display can be performed by using the color filter (colored layer). This is because a broad peak can be modified to be sharp in each emission spectrum of R, G, and B by the color filter (colored layer).

By depositing a material which emits mono-color light and combining with a color filter or a color conversion layer, full color display can be performed. The color filter (colored layer) or the color conversion layer may be provided for, for example, a sealing substrate and attached to an element substrate.

It is needless to say that display of mono-color emission may be performed. For example, an area color type display device may be formed using mono-color emission. The area color type is suitable for a passive matrix display portion and can mainly display characters and/or symbols.

It is necessary that materials for the first electrode layer 870 and the second electrode layer 850 are selected in consideration of the work function. Each of the first electrode layer 870 and the second electrode layer 850 can be either an anode or a cathode depending on the pixel structure. In the case where the conductivity type of a driving thin film transistor is a p-channel type, it is preferable that the first electrode layer 870 be an anode and the second electrode layer 850 be a cathode as shown in FIG. 22A. In the case where the conductivity type of the driving thin film transistor is an n-channel type, it is preferable that the first electrode layer 870 be a cathode and the second electrode layer 850 be an anode as shown in FIG. 22B. Materials that can be used for the first electrode layer 870 and the second electrode layer 850 are described. It is preferable to use a material having a high work function (specifically, a material having a work function of 4.5 eV or more) for one of the first electrode layer 870 and the second electrode layer 850, which serves as an anode, and a material having a low work function (specifically, a material having a work function of 3.5 eV or less) for the other electrode layer which serves as a cathode. However, since the first layer 804 is superior in hole-injecting property and hole-transporting property and the third layer 802 is superior in electron-injecting property and electron transporting property, both the first electrode layer 870 and the second electrode layer 850 are scarcely restricted by a work function and various materials can be used.

The light-emitting elements shown in FIGS. 22A and 22B each have a structure where light is extracted from the first electrode layer 870 and thus, the second electrode layer 850 does not necessarily have a light-transmitting property. The second electrode layer 850 may be formed to a total thickness of 100-800 nm, of a film mainly containing an element selected from titanium, nickel, tungsten, chromium, platinum, zinc, tin, indium, tantalum, aluminum, copper, gold, silver, magnesium, calcium, lithium, and molybdenum, or an alloy material or a compound material containing the above element as its main component, such as titanium nitride, titanium silicon nitride, tungsten silicide, tungsten nitride, tungsten silicon nitride, or niobium nitride, or a stacked-layer film therteof.

Further, also for the first electrode layer 870 and the second electrode layer 850, an evaporation method by resistance heating, an EB evaporation method, a sputtering method, a wet method, or the like can be used. Further, each of the first electrode layer 870 and the second electrode layer 850 may also be formed as follows, as described in Embodiment Mode 3: a conductive light-absorbing film is formed over a transposing substrate and irradiated with laser light, so as to be formed selectively over a transposed substrate while being processed into a desired shape.

Further, when the second electrode layer 850 is formed using a light-transmitting conductive material like the material used for the first electrode layer 870, light can be extracted from the second electrode layer 850 as well, so that a dual emission structure in which light emitted from the light-emitting element is extracted from both of the first electrode layer 870 and the second electrode layer 850 can be obtained.

It is to be noted that the light-emitting element of the present invention can have variations by changing the kinds of the first electrode layer 870 and the second electrode layer 850.

FIG. 22B shows the case where the electroluminescent layer 860 is formed by stacking the third layer 802, the second layer 803, and the first layer 804 sequentially from the first electrode layer 870 side.

FIG. 22C shows the structure in which an electrode layer having light reflectivity is used for the first electrode layer 870 and an electrode layer having a light-transmitting property is used for the second electrode layer 850 in the structure of FIG. 22A, and light emitted from the light-emitting element is reflected on the first electrode layer 870, and transmitted through the second electrode layer 850. Similarly, FIG. 22D shows the structure in which an electrode layer having light reflectivity is used for the first electrode layer 870 and an electrode layer having a light-transmitting property is used for the second electrode layer 850 in the structure of FIG. 22B, and light emitted from the light-emitting element is reflected on the first electrode layer 870, and transmitted through the second electrode layer 850.

As described above, in the light-emitting element of the present invention, the layer interposed between the first electrode layer 870 and the second electrode layer 850 is formed of the electroluminescent layer 860 including a layer in which an organic compound and an inorganic compound are combined. The light-emitting element is an organic-inorganic composite light-emitting element provided with layers (that is, the first layer 804 and the third layer 802) that provide functions of high carrier-injecting property and carrier-transporting property by mixing an organic compound and an inorganic compound. Further, it is particularly necessary that one of the first layer 804 and the third layer 802 which is provided on the first electrode layer 870 side is a layer in which an organic compound and an inorganic compound are combined, and the other which is provided on the second electrode layer 850 side may contain only one of an organic compound and an inorganic compound.

Note that various methods can be used as a method for forming the electroluminescent layer 860 which is the layer in which an organic compound and an inorganic compound are mixed. For example, there is a co-evaporation method in which both an organic compound and an inorganic compound are evaporated by resistance heating. Alternatively, an inorganic compound may be evaporated by an electron beam (EB) while an organic compound is evaporated by resistance heating, to co-evaporate them. Further, there is a method in which sputtering using an inorganic compound is performed while an organic compound is evaporated by resistance heating to deposit them at the same time. Further, the electroluminescent layer 860 may also be formed by a wet method.

This embodiment mode can be freely combined with any of the above embodiment modes each of the display device including the light-emitting element. This embodiment mode can be freely combined with any of Embodiment Modes 1 to 5 as appropriate.

By the present invention, a display device can be manufactured through a simplified process with a complicated photolithography process reduced, so that loss of materials and the cost can be reduced. Therefore, high performance and highly reliable display devices can be manufactured with a high yield.

Embodiment Mode 8

In this embodiment mode, an example of a display device in order to manufacture a display device at low cost through a highly reliable, more simplified process is described. Specifically, a light-emitting display device using a light-emitting element as a display element is described. In this embodiment mode, structures of a light-emitting element applicable as a display element of the display device of the present invention are described with reference to FIGS. 23A to 23C, and 24A to 24C.

A light-emitting element utilizing electroluminescence is distinguished depending on whether a light-emitting material is an organic compound or an inorganic compound. In general, the former is called an organic EL element, and the latter is called an inorganic EL element.

The inorganic EL element is categorized into a dispersion inorganic EL element and a thin-film inorganic EL element depending on its element structure. The former and the latter are different in that the former has an electroluminescent layer where particles of a light-emitting material are dispersed in a binder whereas the latter has an electroluminescent layer formed of a thin film of a light-emitting material. However, the former and the latter are the same in that electrons accelerated by a high electric field are necessary. Note that, as a mechanism of light emission obtained, there are donor-acceptor recombination light emission that utilizes a donor level and an acceptor level, and localized light emission that utilizes inner-shell electron transition of a metal ion. In general, a dispersion inorganic EL element may have donor-acceptor recombination light emission and a thin-film inorganic EL element may have localized light emission.

The light-emitting material that can be used in the present invention includes a base material and an impurity element to be a light-emission center. By changing an impurity element that is contained, light emission of various colors can be obtained. As a method for forming the light-emitting material, various methods such as a solid phase method and a liquid phase method (a coprecipitation method) may be used. Alternatively, an evaporative decomposition method, a double decomposition method, a method by heat decomposition reaction of a precursor, a reversed micelle method, a method in which such a method is combined with high-temperature baking, a liquid phase method such as a lyophilization method, or the like can be used.

A solid phase method is a method in which a base material, and an impurity element or a compound containing an impurity element are weighed, mixed in a mortar, heated in an electric furnace, and baked to be reacted, so that the impurity element is contained in the base material. The baking temperature is preferably 700-1500° C. This is because the solid reaction does not progress when the temperature is too low, whereas the base material is decomposed when the temperature is too high. The baking may be performed in a powder state; however, it is preferable to perform the baking in a pellet state. Although the baking is necessarily performed at relatively high temperature, the solid phase method is easy; therefore, high productivity can be achieved. Thus, the solid phase method is suitable for mass production.

A liquid phase method (a coprecipitation method) is a method in which a base material or a compound containing a base material is reacted with an impurity element or a compound containing an impurity element in a solution, dried, and then baked. Particles of a light-emitting material are distributed uniformly, and the reaction can progress even when the grain size is small and the baking temperature is low.

As the base material used for the light-emitting material, sulfide, oxide, or nitride can be used. As sulfide, the following can be used: zinc sulfide (ZnS), cadmium sulfide (CdS), calcium sulfide (CaS), yttrium sulfide (Y₂S₃), gallium sulfide (Ga₂S₃), strontium sulfide (SrS), barium sulfide (BaS), or the like. As oxide, zinc oxide (ZnO), yttrium oxide (Y₂O₃), or the like can be used. As nitride, aluminum nitride (AIN), gallium nitride (GaN), indium nitride (InN), or the like can be used. Alternatively, zinc selenide (ZnSe), zinc telluride (ZnTe), or the like may be used, or a ternary mixed crystal such as calcium gallium sulfide (CaGa₂S₄), strontium gallium sulfide (SrGa₂S₄), or barium gallium sulfide (BaGa₂S₄) may be used.

As the light-emission center of localized light emission, the following can be used: manganese (Mn), copper (Cu), samarium (Sm), terbium (Th), erbium (Er), thulium (Tm), europium (Eu), cerium (Ce), praseodymium (Pr), or the like. Note that a halogen element such as fluorine (F) or chlorine (Cl) may be added. The halogen element can also function as charge compensation.

On the other hand, as the light-emission center of donor-acceptor recombination light emission, a light-emitting material containing a first impurity element which forms a donor level and a second impurity element which forms an acceptor level can be used. As the first impurity element, fluorine (F), chlorine (Cl), aluminum (Al), or the like can be used. As the second impurity element, copper (Cu), silver (Ag), or the like can be used.

In the case where the light-emitting material of donor-acceptor recombination light emission is synthesized by a solid phase method, each of the base material, the first impurity element or a compound containing the first impurity element, and the second impurity element or a compound containing the second impurity element is weighed, mixed in a mortar, heated in an electric furnace, and baked. As the base material, any of the above-described base materials can be used. As the first impurity element or the compound containing the first impurity element, fluorine (F), chlorine (Cl), aluminum sulfide (Al₂S₃), or the like can be used. As the second impurity element or the compound containing the second impurity element, copper (Cu), silver (Ag), copper sulfide (Cu₂S), silver sulfide (Ag₂S), or the like can be used. The baking temperature is preferably 700-1500° C. This is because the solid reaction does not progress when the temperature is too low, whereas the base material is decomposed when the temperature is too high. The baking may be performed in a powder state; however, it is preferable to perform the baking in a pellet state.

As the impurity element in the case of utilizing solid reaction, the compounds containing the first impurity element and the second impurity element may be combined. In this case, since the impurity elements are easily diffused and solid reaction progresses easily, a uniform light-emitting material can be obtained. Further, since an unnecessary impurity element is not mixed, a light-emitting material having high purity can be obtained. As the compound containing the first impurity element and the second impurity element, copper chloride (CuCL), silver chloride (AgCl), or the like can be used.

Note that the concentration of these impurity elements may be 0.01-10 atomic % with respect to the base material and is preferably 0.05-5 atomic %.

In the case of a thin-film inorganic EL element, an electroluminescent layer is a layer containing the above light-emitting material, and can be formed by a vacuum evaporation method such as a resistance heating evaporation method or an electron beam evaporation (EB evaporation) method, a physical vapor deposition (PVD) method such as a sputtering method, a chemical vapor deposition (CVD) method such as a metal organic CVD method or a low-pressure hydride transport CVD method, an atomic layer epitaxy (ALE) method, or the like.

FIGS. 23A to 23C each show an example of a thin-film inorganic EL element that can be used as a light-emitting element. In FIGS. 23A to 23C, each light-emitting element includes a first electrode layer 50, an electroluminescent layer 52, and a second electrode layer 53.

The light-emitting elements shown in FIGS. 23B and 23C each have a structure where an insulating layer is provided between the electrode layer and the electroluminescent layer of the light-emitting element of FIG. 23A. The light-emitting element shown in FIG. 23B has an insulating layer 54 between the first electrode layer 50 and the electroluminescent layer 52. The light-emitting element shown in FIG. 23C includes an insulating layer 54 a between the first electrode layer 50 and the electroluminescent layer 52, and an insulating layer 54 b between the second electrode layer 53 and the electroluminescent layer 52. Thus, the insulating layer may be provided either between the electroluminescent layer and one of the electrode layers that interpose the electroluminescent layer, or both of between the electroluminescent layer and the first electrode layer and between the electroluminescent layer and the second electrode layer. Further, the insulating layer may employ a single-layer structure or a stacked-layer structure including a plurality of layers.

Further, although the insulating layer 54 is provided so as to be in contact with the first electrode layer 50 in FIG. 23B, the insulating layer 54 may be provided so as to be in contact with the second electrode layer 53 by reversing the order of the insulating layer and the electroluminescent layer.

In the case of a dispersion inorganic EL element, a film-shaped electroluminescent layer is formed by dispersing particles of a light-emitting material in a binder. When particles with a desired grain size cannot be obtained by a method for manufacturing a light-emitting material, a light-emitting material may be processed into a particle state by crushing in a mortar or the like. The binder is a substance for fixing particles of a light-emitting material in a dispersed state to keep a shape of an electroluminescent layer. The light-emitting material is uniformly dispersed and fixed in the electroluminescent layer by the binder.

In the case of the dispersion inorganic EL element, as a method for forming an electroluminescent layer, a droplet discharging method which can selectively form an electroluminescent layer, a printing method (such as screen printing or offset printing), a coating method such as a spin coating method, a dipping method, a dispenser method, or the like can be used. There is no particular limitation on the thickness of the electroluminescent layer; however, a thickness of 10-1000 nm is preferable. In addition, in the electroluminescent layer containing a light-emitting material and a binder, a ratio of the light-emitting material is preferably equal to or greater than 50 wt % and equal to or less than 80 wt %.

FIGS. 24A to 24C each show an example of a dispersion inorganic EL element that can be used as a light-emitting element. A light-emitting element shown in FIG. 24A employs a stacked-layer structure of a first electrode layer 60, an electroluminescent layer 62, and a second electrode layer 63, in which a light-emitting material 61 held by a binder is contained in the electroluminescent layer 62.

Further, also each of the first electrode layers 50 and 60 and the second electrode layers 53 and 63 may be formed as follows, as described in Embodiment Mode 3: a conductive light-absorbing film is formed over a transposing substrate and irradiated with laser light, so as to be formed selectively over a transposed substrate while being processed into a desired shape.

As the binder that can be used in this embodiment mode, an organic material or an inorganic material can be used, and a mixed material of an organic material and an inorganic material may also be used. As the organic material, a resin such as a polymer having a relatively high dielectric constant, e.g., a cyanoethyl cellulose-based resin, polyethylene, polypropylene, a polystyrene-based resin, a silicone resin, an epoxy resin, or vinylidene fluoride can be used. Alternatively, a heat-resistant high molecular such as aromatic polyamide or polybenzimidazole, or a siloxane resin may be used. Note that a siloxane resin corresponds to a resin containing a Si—O—Si bond. Siloxane is composed of a skeleton structure including a bond of silicon (Si) and oxygen (O). As a substituent thereof, an organic group containing at least hydrogen (such as an alkyl group or aromatic hydrocarbon) is used. Instead, a fluoro group, or a fluoro group and an organic group containing at least hydrogen may be used as the substituent. Further alternatively, a resin material such as a vinyl resin, e.g., polyvinyl alcohol or polyvinyl butyral, a phenol resin, a novolac resin, an acrylic resin, a melamine resin, a urethane resin, or an oxazole resin (polybenzoxazole) may be used. A dielectric constant can be controlled by mixing high-dielectric constant microparticles of barium titanate (BaTiO₃), strontium titanate (SrTiO₃), or the like as appropriate.

As the inorganic material contained in the binder, a material selected from silicon oxide (SiO_(x)), silicon nitride (SiN_(x)), silicon containing oxygen and nitrogen, aluminum nitride (AlN), aluminum containing oxygen and nitrogen, aluminum oxide (Al₂O₃), titanium oxide (TiO₂), BaTiO₃, SrTiO₃, lead titanate (PbTiO₃), potassium niobate (KNbO₃), lead niobate (PbNbO₃), tantalum oxide (Ta₂O₅), barium tantalate (BaTa₂O₆), lithium tantalate (LiTaO₃), yttrium oxide (Y₂O₃), zirconium oxide (ZrO₂), and other substances containing an inorganic material can be used. By mixing a high-dielectric constant inorganic material (by addition or the like), a dielectric constant of an electroluminescent layer containing a light-emitting material and a binder can be further controlled to be increased. When a mixed layer of an inorganic material and an organic material is used for the binder to provide a high dielectric constant, a large amount of electric charges can be induced by the light-emitting material.

In a manufacturing process, the light-emitting material is dispersed in a solution containing a binder. As a solvent of the solution containing the binder that can be used in this embodiment mode, it is preferable to select a solvent that dissolves a binder material and can make a solution with the viscosity appropriate for a method for forming the electroluminescent layer (various wet processes) and a desired film thickness. An organic solvent or the like can be used, and for example, when a siloxane resin is used as the binder, propylene glycolmonomethyl ether, propylene glycolmonomethyl ether acetate (also called PGMEA), 3-methoxy-3-methyl-1-butanol (also called MMB), or the like can be used.

Light-emitting elements shown in FIGS. 24B and 24C each have a structure where an insulating layer is provided between the electrode layer and the electroluminescent layer of the light-emitting element of FIG. 24A. The light-emitting element shown in FIG. 24B has an insulating layer 64 between the first electrode layer 60 and the electroluminescent layer 62. The light-emitting element shown in FIG. 24C includes an insulating layer 64 a between the first electrode layer 60 and the electroluminescent layer 62, and an insulating layer 64 b between the second electrode layer 63 and the electroluminescent layer 62. Thus, the insulating layer may be provided either between the electroluminescent layer and one of the electrode layers that interpose the electroluminescent layer, or both of between the electroluminescent layer and the first electrode layer and between the electroluminescent layer and the second electrode layer. Further, the insulating layer may employ a single-layer structure or a stacked-layer structure including a plurality of layers.

Further, although the insulating layer 64 is provided so as to be in contact with the first electrode layer 60 in FIG. 24B, the insulating layer 64 may be provided so as to be in contact with the second electrode layer 63 by reversing the order of the insulating layer and the electroluminescent layer.

Although the insulating layer 54 in FIGS. 23B and 23C and the insulating layer 64 in FIGS. 24B and 24C are not particularly limited, such insulating layers preferably have high dielectric strength and dense film qualities, and more preferably have a high dielectric constant. For example, silicon oxide (SiO₂), yttrium oxide (Y₂O₃), titanium oxide (TiO₂), aluminum oxide (Al₂O₃), hafnium oxide (HfO₂), tantalum oxide (Ta₂O₅), barium titanate (BaTiO₃), strontium titanate (SrTiO₃), lead titanate (PbTiO₃), silicon nitride (Si₃N₄), zirconium oxide (ZrO₂), or the like, or a mixed film or a staked-layer film of two or more kinds thereof can be used. Such an insulating film can be formed by sputtering, evaporation, CVD, or the like. Further, the insulating layer may also be formed by dispersing particles of such an insulating material in a binder. A binder material may be formed of a similar material and by a similar method to the binder contained in the electroluminescent layer. A thickness of such an insulating layer is not particularly limited, and is preferably in the range of 10-1000 mn.

Each light-emitting element described in this embodiment mode can emit light by application of voltage between the pair of electrode layers which interpose the electroluminescent layer, and can be operated by either direct current driving or alternating current driving.

By the present invention, a display device can be manufactured through a simplified process with a complicated photolithography process reduced, so that loss of materials and the cost can be reduced. Therefore, high performance and highly reliable display devices can be manufactured with a high yield.

This embodiment mode can be freely combined with any of Embodiment Modes 1 to 5 as appropriate.

Embodiment Mode 9

In this embodiment mode, an example of a display device in order to manufacture a display device at low cost through a highly reliable, more simplified process is described. Specifically, a liquid crystal display device using a liquid crystal display element as a display element is described.

FIG. 19A is a top diagram of a liquid crystal display device, and FIG. 19B is a cross-sectional diagram taken along line G-H of FIG. 19A.

As shown in FIG. 19A, a pixel region 606, and driver circuit regions 608 a and 608 b which are scan line driver circuits are sealed between a substrate 600 and a counter substrate 695 with a sealing member 692, and a driver circuit region 607 which is a signal line driver circuit formed of an IC driver is provided over the substrate 600. A transistor 622 and a capacitor 623 are provided in the pixel region 606. A driver circuit including transistors 620 and 621 is provided in the driver circuit region 608 b. An insulating substrate can be used as the substrate 600 as in the above embodiment modes. Further, although there is a general concern that a substrate formed of a synthetic resin has a lower temperature limit than other substrates, the substrate formed of the synthetic resin can be used by transposition after a manufacturing process is performed using a substrate with high heat resistance. Note that in the drawing, reference numeral 602 denotes an external terminal connection region and reference numeral 603 denotes a sealing region.

In the pixel region 606, the transistor 622 which is to be a switching element is provided with base films 604 a and 604 b interposed therebetween. In this embodiment mode, a multi-gate thin film transistor (TFT) is used as the transistor 622, which includes a semiconductor layer having impurity regions serving as a source region and a drain region, a gate insulting layer, a gate electrode layer having a stacked-layer structure of two layers, a source electrode layer, and a drain electrode layer. The source or drain electrode layer is in contact with and electrically connected to the impurity region of the semiconductor layer and a pixel electrode layer 630.

Each of the source electrode layer and the drain electrode layer has a stacked-layer structure, and source and drain electrode layers 644 a and 644 b are electrically connected to the pixel electrode layer 630 in an opening formed in an insulating layer 615. The opening in the insulating layer 615 can be formed by irradiation with laser light as described in Embodiment Mode 1. In this embodiment mode, the source or drain electrode layer 644 b is formed using a low-melting point metal that is relatively easily evaporated (chromium in this embodiment mode), and the source or drain electrode layer 644 a is formed using a high-melting point metal that is not easily evaporated compared to the source or drain electrode layer 644 b (tungsten in this embodiment mode). The source and drain electrode layers 644 a and 644 b are selectively irradiated with laser light from the insulating layer 615 side, and then the insulating layer 615 above an irradiated region of the source or drain electrode layer 644 b is removed by the irradiation energy, so that an opening reaching the source or drain electrode layer 644 b is formed. A shape of the opening can be controlled by an irradiated region (spot) of laser light and shapes of the source electrode layer and drain electrode layer to which laser light irradiation is performed. The pixel electrode layer 630 is formed in the opening where the source electrode layer and drain electrode layer 644 a and 644 b are exposed, thereby electrically connected to the source electrode layer and drain electrode layer 644 a and 644 b.

The thin film transistor can be manufactured by various methods. For example, a crystalline semiconductor film is used as an active layer, a gate electrode is provided over the crystalline semiconductor film with a gate insulating film interposed therebetween, and an impurity element can be added to the active layer by using the gate electrode. Thus, by using the gate electrode for adding the impurity element, it is not necessary to form a mask for adding the impurity element. The gate electrode can employ a single-layer structure or a stacked-layer structure. The impurity region can be either a high-concentration impurity region or a low-concentration impurity region with its concentration being controlled. A structure of such a thin film transistor having a low-concentration impurity region is called an LDD (Lightly Doped Drain) structure. Further, the low-concentration impurity region may be formed so as to overlap with the gate electrode and a structure of such a thin film transistor is called a GOLD (Gate Overlapped LDD) structure. The conductivity type of the thin film transistor is an n type when phosphorus (P) or the like is used for the impurity region. The conductivity type of the thin film transistor is a p type when boron (B) or the like is added. After that, insulating films 611 and 612 covering the gate electrode and the like are formed. A dangling bond of the crystalline semiconductor film can be terminated by a hydrogen element mixed into the insulating film 611(and the insulating film 612).

In order to further improve planarity, the insulating layer 615 may be formed as an interlayer insulating layer. As the insulating layer 615, an organic material, an inorganic material, or a stacked-layer structure thereof can be used. For example, a material selected from silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, aluminum nitride, aluminum oxynitride, aluminum nitride oxide containing more nitrogen than oxygen, aluminum oxide, diamond-like carbon (DLC), polysilazane, nitrogen-containing carbon (CN), PSG (phosphosilicate glass), BPSG (borophosphosilicate glass), alumina, and other substances containing an inorganic insulating materials can be used. Alternatively, an organic insulating material may be used. As the organic material, either a photosensitive material or a nonphotosensitive material can be used, and polyimide, acrylic, polyamide, polyimide amide, resist, benzocyclobutene, a siloxane resin, or the like can be used. It is to be noted that a siloxane resin is a resin containing a Si—O—Si bond. The skeleton structure of siloxane is formed of a bond of silicon (Si) and oxygen (O). As a substituent, an organic group containing at least hydrogen (such as an alkyl group or aromatic hydrocarbon) is used. Instead, a fluoro group, or a fluoro group and an organic group containing at least hydrogen may be used as the substituent.

The pixel region and the driver circuit region can be formed over the same substrate when the crystalline semiconductor film is used. In this case, each transistor in the pixel region and each transistor in the driver circuit region 608 b are formed at the same time. The transistors included in the driver circuit region 608 b forms a CMOS circuit. Although each thin film transistor included in the CMOS circuit employs a GOLD structure, it may employ an LDD structure like the transistor 622.

The present invention is not limited to this embodiment mode, and each thin film transistor in the pixel region may employ any of a single-gate structure in which one channel formation region is formed, a double-gate structure in which two channel formation regions are formed, and a triple-gate structure in which three channel formation regions are formed. Similarly, each thin film transistor in the peripheral driver circuit region may employ any of a single-gate structure, a double-gate structure, and a triple-gate structure.

Note that the present invention is not limited to each thin film transistor described in this embodiment mode. The present invention may also be applied to a thin film transistor employing any of a top gate structure (e.g., a staggered type), a bottom gate structure (e.g., an inversely staggered type), a dual gate structure in which two gate electrode layers are arranged above and below a channel formation region, with a gate insulating film interposed between the channel formation region and each gate electrode layer, and other structures.

Next, an insulating layer 631 called an alignment film is formed by a printing method or a droplet discharging method so as to cover the pixel electrode layer 630. Note that the insulating layer 631 can be selectively formed by a screen printing method or an off-set printing method. Thereafter, rubbing treatment is performed. This rubbing treatment is not performed in some cases where a liquid crystal mode is, for example, a VA mode. An insulating layer 633 serving as an alignment film is similar to the insulating layer 631. Then, the sealing member 692 is formed in a peripheral region of the pixels by a droplet discharging method.

After that, the counter substrate 695 provided with the insulating layer 633 serving as the alignment film, a conductive layer 634 serving as a counter electrode, a colored layer 635 serving as a color filter, a polarizer 641 (also called a polarizing plate), and a polarizer 642 is attached to the substrate 600 which is the TFT substrate with a spacer 637 interposed therebetween, and a liquid crystal layer 632 is provided in the space therebetween. Since the liquid crystal display device of this embodiment mode is a transmissive type, a polarizer (polarizing plate) 643 is also provided on the side of the substrate 600, which is opposite to the side where the elements are provided. The polarizer can be provided over the substrate with the use of an adhesive layer. A filler may be mixed into the sealing member, and a light-shielding film (a black matrix) or the like may be provided for the counter substrate 695. Note that the color filter or the like may be formed of materials which exhibit red (R), green (G), and blue (B) when the liquid crystal display device performs full-color display, and may be omitted or may be formed of a material which exhibits at least one color when the liquid crystal display device performs a mono-color display.

Note that when light-emitting diodes (LEDs) which exhibit R, G and B respectively, or the like are provided as backlights and a field sequential method for performing color display by time division is employed, there is the case where the color filter is not provided. The black matrix may be provided so as to overlap the transistor and the CMOS circuit in order to reduce the reflection of external light due to a wiring of the transistor and the CMOS circuit. Note that the black matrix may be provided so as to overlap the capacitor; this is because the black matrix can prevent reflection due to a metal film included in the capacitor.

As a method for forming the liquid crystal layer, a dispenser method (a dripping method) can be employed, or an injection method in which a liquid crystal is injected with the use of a capillary phenomenon may be used after the substrate 600 provided with the elements is attached to the counter substrate 695. The dripping method may be employed when a large substrate to which the injection method is difficult to be applied is used.

The spacer may be provided by a method of spraying particles each having a size of several μm. In this embodiment mode, a method in which a resin film is formed over the entire surface of the substrate and then etched is employed. A material for the spacer is applied by a spinner and then, light exposure and developing treatment are performed to form a predetermined pattern thereof. Further, the material is heated at 150-200° C. in a clean oven or the like to be cured. The spacer thus manufactured can have various shapes depending on the conditions of the light exposure and the developing treatment. It is preferable that the spacer have a columnar shape with a flat top so that mechanical strength of the liquid crystal display device can be secured when the counter substrate is attached. The shape of the spacer is not particularly limited and may be conical, pyramidal, or the like.

Then, an FPC 694, which is a wiring board for connection, is provided over terminal electrode layers 678 a and 678 b electrically connected to the pixel region, with an anisotropic conductive layer 696 interposed therebetween. The FPC 694 transmits signals and potentials from outside. Through the above-described steps, a liquid crystal display device having a display function can be manufactured.

Note that as each of the wiring, the gate electrode layer, the pixel electrode layer 630, and the conductive layer 634 serving as the counter electrode layer included in the transistor, the following can be used: indium tin oxide (ITO), indium zinc oxide (IZO) in which zinc oxide (ZnO) is mixed with indium oxide, a conductive material in which silicon oxide (SiO₂) is mixed with indium oxide, organic indium, organic tin, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide; a metal such as tungsten (W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel (Ni), titanium (Ti), platinum (Pt), aluminum (Al), copper (Cu), or silver (Ag); an alloy of such a metal; or metal nitride thereof.

A retardation film may be provided between the polarizing plate and the liquid crystal layer.

Note that although this embodiment mode describes a TN liquid crystal panel, the above process can also be applied similarly to liquid crystal panels of other modes. For example, this embodiment mode can be applied to a liquid crystal panel of a transverse electric field mode in which liquid crystals are aligned by application of an electric filed in a direction parallel to the glass substrate. Further, this embodiment mode can also be applied to a VA (Vertical Alignment) mode liquid crystal panel.

FIGS. 5 and 6 show a pixel structure of a VA liquid crystal panel. FIG. 5 is a plan diagram, and FIG. 6 shows a cross-sectional structure taken along line I-J in FIG. 5. In the following description, these drawings are used.

In this pixel structure, a plurality of pixel electrodes are provided for one pixel, and each pixel electrode is connected to a TFT. Each TFT is driven by a different gate signal. That is, in a multi-domain pixel, respective signals applied to pixel electrodes are controlled separately.

A pixel electrode layer 1624 is connected to a TFT 1628 with a wiring layer 1618 in an opening (a contact hole) 1623. In addition, a pixel electrode layer 1626 is connected to a TFT 1629 with a wiring layer 1619 in an opening (a contact hole) 1627. A gate wiring layer 1602 of the TFT 1628 and a gate electrode layer 1603 of the TFT 1629 are separated such that different gate signals are supplied. On the other hand, a wiring layer 1616 functioning as a data line is used in common in the TFTs 1628 and 1629.

Each of the pixel electrode layers 1624 and 1626 may also be formed as follows, as described in Embodiment Mode 3: a conductive light-absorbing film is formed over a transposing substrate, and irradiated with laser light, so as to be formed selectively over a transposed substrate while being processed into a desired shape. Accordingly, by using the present invention, since the manufacturing process is simplified and loss of materials can be prevented, a display device can be manufactured at low cost with high productivity.

Shapes of the pixel electrode layers 1624 and 1626 are different, and the pixel electrode layers 1624 and 1626 are separated by a slit 1625. The pixel electrode layer 1626 is formed so as to surround the pixel electrode layer 1624 that spreads out into a V-shape. Timings of application of voltage to the pixel electrode layers 1624 and 1626 are made different in the TFTs 1628 and 1629, thereby controlling alignment of liquid crystals 1650. A light-shielding film 1632, a colored layer 1636, and a counter electrode layer 1640 are provided for a counter substrate 1601. A planarization film 1637 is formed between the colored layer 1636 and the counter electrode layer 1640 so that disordered alignment of the liquid crystals 1650 is prevented.

Note that in FIG. 6, reference numeral 1600 denotes a substrate, 1606 denotes a gate insulating layer, 1609 denotes a semiconductor layer, 1610 and 1611 denote semiconductor layers having one conductivity type, 1620 and 1622 denote insulating layers, and 1646 and 1648 denote alignment films.

FIG. 7 shows a structure of the counter substrate side. The counter electrode layer 1640 is used in common for different pixels, and a slit 1641 is formed. The slit 1641 and the slit 1625 on the side of the pixel electrode layers 1624 and 1626 are arranged so as to interdigitate, so that an oblique electric field can be effectively generated to control alignment of liquid crystals. Accordingly, an alignment direction of the liquid crystals can be varied depending on a position, so that the viewing angle can be widened.

Thus, a liquid crystal panel can be manufactured using a composite material of an organic compound and an inorganic compound as a pixel electrode layer. With the use of such a pixel electrode, it is not necessary to use a transparent conductive film containing indium as its main component and a material bottleneck can be resolved.

This embodiment mode can be freely combined with any of Embodiment Modes 1 to 3 as appropriate.

By the present invention, a display device can be manufactured through a simplified process with a complicated photolithography process reduced, so that loss of materials and the cost can be reduced. Therefore, high performance and highly reliable display devices can be manufactured with a high yield.

Embodiment Mode 10

In this embodiment mode, an example of a display device in order to manufacture a display device at low cost through a highly reliable, more simplified process is described. Specifically, a liquid crystal display device using a liquid crystal display element as a display element is described.

In a display device shown in FIG. 18, a transistor 220 which is an inversely staggered thin film transistor, a pixel electrode layer 251, an insulating layer 252, an insulating layer 253, a liquid crystal layer 254, a spacer 281, an insulating layer 235, a counter electrode layer 256, a color filter 258, a black matrix 257, a counter substrate 210, a polarizing plate (a polarizer) 231, and a polarizing plate (a polarizer) 233 are provided in a pixel region, and a sealing member 282, a terminal electrode layer 287, an anisotropic conductive layer 288, and an FPC 286 are provided in a sealing region, over a substrate 250.

Each of a gate electrode layer, a semiconductor layer, a source electrode layer, a drain electrode layer, and the pixel electrode layer 251 of the transistor 220 which is an inversely staggered thin film transistor formed in this embodiment mode may also be formed as follows, as described in Embodiment Mode 3: a light-absorbing film using a conductive material or a semiconductor material is formed over a transposing substrate, and irradiated with laser light, so as to be formed selectively over a transposed substrate while being processed into a desired shape. Accordingly, by using the present invention, since the manufacturing process is simplified and loss of materials can be prevented, a display device can be manufactured at low cost with high productivity.

In this embodiment mode, an amorphous semiconductor is used as the semiconductor layer, and the semiconductor layer having one conductivity type may be formed as needed. In this embodiment mode, the semiconductor layer and an amorphous n-type semiconductor layer as the semiconductor layer having one conductivity type are stacked. Further, an NMOS structure of an n-channel thin film transistor can be formed by forming an n-type semiconductor layer, a PMOS structure of a p-channel thin film transistor can be formed by forming a p-type semiconductor layer, or a CMOS structure of an n-channel thin film transistor and a p-channel thin film transistor can be formed.

Further, in order to impart a conductivity type, an element imparting conductivity type may be added by doping to form an impurity region in the semiconductor layer, so that an n-channel thin film transistor or a p-channel thin film transistor can be formed. Instead of forming an n-type semiconductor layer, a conductivity type may be imparted to the semiconductor layer by plasma treatment using a PH₃ gas.

In this embodiment mode, the transistor 220 is an n-channel inversely staggered thin film transistor. Alternatively, a channel protective type, inversely staggered thin film transistor in which a protective layer is provided over a channel region of the semiconductor layer may be used.

Next, a structure of a backlight unit 352 is described. The backlight unit 352 includes a cold cathode tube, a hot cathode tube, a light-emitting diode, an inorganic EL, or an organic EL as a light source 361 which emits fluorescence, a lamp reflector 362 for effectively leading fluorescence to a light guide plate 365, the light guide plate 365 for leading light to the entire surface with fluorescence totally reflected, a diffusing plate 366 for reducing variations in brightness, and a reflective plate 364 for reusing light leaked under the light guide plate 365.

A control circuit for adjusting the luminance of the light source 361 is connected to the backlight unit 352. The luminance of the light source 361 can be controlled by a signal supplied from the control circuit.

The source or drain electrode layer of the transistor 220 is electrically connected to the pixel electrode layer 251 in an opening formed in the insulating layer 252. The opening formed in the insulating layer 252 can be formed by irradiation with laser light as described in Embodiment Mode 1. In this embodiment mode, the source or drain electrode layer is formed of a low-melting point metal that is relatively easily evaporated (chromium in this embodiment mode). The source or drain electrode layer is selectively irradiated with laser light from the insulating layer 252 side, so that the insulating layer 252 above an irradiated region of the source or drain electrode layer is removed by the irradiation energy, to form an opening. A shape of the opening can be controlled by the irradiated region (spot) of laser light and a shape of the source or drain electrode layer to which laser light irradiation is performed. The pixel electrode layer 251 is formed in the opening where the source or drain electrode layer is exposed, thereby electrically connected to the source or drain electrode layer.

This embodiment mode can be combined with any of Embodiment Modes 1 to 3 as appropriate.

By the present invention, a display device can be manufactured through a simplified process with a complicated photolithography process reduced, so that loss of materials and the cost can be reduced. Therefore, high performance and highly reliable display devices can be manufactured with a high yield.

Embodiment Mode 11

In this embodiment mode, an example of a display device in order to manufacture a display device at low cost through a highly reliable, more simplified process is described.

FIG. 21 shows active matrix electronic paper to which the present invention is applied. Although FIG. 21 shows an active matrix type one, the present invention can also be applied to a passive matrix type one.

A twist ball display mode can be used for the electronic paper. A twist ball display mode is a method in which spherical particles each colored in black and white are arranged between a first electrode layer and a second electrode layer, and a potential difference is generated between the first electrode layer and the second electrode layer to control directions of the spherical particles, so that display is performed.

A transistor 581 is an inverse coplanar type thin film transistor, and includes a gate electrode layer 582, a gate insulating layer 584, wiring layers 585 a and 585 b, and a semiconductor layer 586. In addition, the wiring layer 585 b is in contact with and electrically connected to a first electrode layer 587 a in an opening formed in an insulating layer 598. Between the first electrode layer 587 a and a first electrode layer 587 b, and a second electrode layer 588, spherical particles 589 each including a black region 590 a and a white region 590 b, and a cavity 594 filled with liquid around the black and white regions 590 a and 590 b, are provided, and the space on the periphery of the spherical particles 589 is filled with a filler 595 such as a resin or the like (see FIG. 21). Note that in the drawing, reference numerals 580 and 596 denote substrates.

In this embodiment mode, each of the gate electrode layer, the semiconductor layer, the source electrode layer, the drain electrode layer, the electrode layer, and the like may also be formed as follows, as described in Embodiment Mode 3: a conductive light-absorbing film is formed over a transposing substrate, and irradiated with laser light, so as to be formed selectively over a transposed substrate while being processed into a desired shape. Accordingly, by using the present invention, since the manufacturing process is simplified and loss of materials can be prevented, cost can be realized.

The wiring layer 585 b is electrically connected to the first electrode layer 587 a in the opening formed in the insulating layer 598. The opening formed in the insulating layer 598 can be formed by irradiation with laser light as described in Embodiment Mode 1. In this embodiment mode, the wiring layer 585 b is formed of a low-melting point metal that is relatively easily evaporated (chromium in this embodiment mode). The wiring layer 585 b is selectively irradiated with laser light from the insulating layer 598 side, so that the insulating layer 598 above an irradiated region of the wiring layer 585 b is removed by the irradiation energy, to form an opening. A shape of the opening can be controlled by the irradiated region (spot) of laser light and a shape of the wiring layer 585 b to which laser light irradiation is performed. The first electrode layer 587 a is formed in the opening where the wiring layer 585 b is exposed, thereby electrically connected to the first electrode layer 587 a.

Instead of the twist ball, an electrophoretic element may be used. A microcapsule having a diameter of 10-20μm in which transparent liquid, positively charged white microparticles, and negatively charged black microparticles are encapsulated is used. In the microcapsule provided between the first electrode layer and the second electrode layer, when an electric field is applied by the first electrode layer and the second electrode layer, the white microparticles and black microparticles move in opposite directions from each other, so that white or black can be displayed. A display element using this principle is an electrophoretic display element and is called electronic paper in general. The electrophoretic display element has higher reflectivity than a liquid crystal display element, and thus an assistant light is unnecessary, power consumption is low, and a display portion can be recognized even in a dim place. Further, even when electric power is not supplied to the display portion, an image which has been displayed once can be stored. Thus, a displayed image can be stored even if a display device having a display function is distanced from a source of an electronic wave.

The transistor may employ any structure as long as the transistor can function as a switching element. As the semiconductor layer, various semiconductors such as an amorphous semiconductor, a crystalline semiconductor, a polycrystalline semiconductor, and a microcrystal semiconductor may be used, or an organic transistor may be formed using an organic compound.

Although this embodiment mode specifically describes the case where a structure of a display device is an active matrix type, it is needless to say that the present invention can also be applied to a passive matrix display device. Also in a passive matrix display device, each of a wiring layer, an electrode layer, and the like may be formed as follows: a conductive light-absorbing film is formed over a transposing substrate, and irradiated with laser light, so as to be formed selectively over a transposed substrate while being processed into a desired shape.

This embodiment mode can be combined with freely any of Embodiment Modes 1 to 3 as appropriate.

By the present invention, a display device can be manufactured through a simplified process with a complicated photolithography process reduced, so that loss of materials and the cost can be reduced. Therefore, high performance and highly reliable display devices can be manufactured with a high yield.

Embodiment Mode 12

Next, modes of mounting a driver circuit on a display panel manufactured in accordance with each of Embodiment Modes 4 to 11 are described.

First, a display device employing a COG method is described with reference to FIG. 25A. The pixel portion 2701 for displaying information such as characters, images, or the like is provided over the substrate 2700. A substrate provided with a plurality of driver circuits is divided into rectangles, and each driver circuit (also referred to as a driver IC) 2751 after division is mounted on the substrate 2700. FIG. 26A shows a mode of mounting a plurality of driver ICs 2751 and FPCs 2750 on the tips of the driver ICs 2751. In addition, the size obtained by division may be made almost the same as the length of a side of the pixel region on a signal line side, and a tape may be mounted on the tip of each single driver IC.

Alternatively, a TAB method may be employed. In this case, as shown in FIG. 26B, a plurality of tapes may be attached, and driver ICs may be mounted on the tapes. Similarly to the case of the COG method, a single driver IC may be mounted on a single tape. In this case, a metal piece or the like for fixing the driver IC is preferably attached together for the strength.

As for such a driver IC to be mounted on the display panel, it is preferable to manufacture a plurality of driver ICs over a rectangular substrate having a side length of 300-1000 mm or larger than 1000 mm for improvement in productivity.

That is, a plurality of circuit patterns each including a driver circuit portion and an input/output terminal as one unit may be formed over a substrate and then divided to be taken out. In consideration of the side length of the pixel portion or the pixel pitch, the driver IC may be formed to be a rectangle having a long side length of 15-80 mm and a short side length of 1-6 mm. Alternatively, the driver IC may be formed to have the side length that is the same as that of the pixel portion, or the length obtained by addition of a side length of the pixel region and a side length of each driver circuit.

An advantage of the external dimension of the driver IC over an IC chip is the length of the long side. When the driver IC having a long side length of 15-80 mm is used, the number of driver ICs necessary for being mounted in accordance with the pixel region is smaller than that in the case of using an IC chip. Therefore, the yield in manufacturing can be improved. Further, when a driver IC is formed over a glass substrate, there is no limitation on the shape of the substrate used as a base; therefore, productivity is not decreased. This is a great advantage compared to the case where IC chips are taken out of a circular silicon wafer.

Further, in the case where the scan line driver circuit 3702 is formed over the same substrate as the pixel region 3701 as shown in FIG. 25B, a driver IC in which a signal line driver circuit is formed is mounted on a region outside the pixel region 3701. The driver IC is a signal line driver circuit. In order to form a pixel portion corresponding to RGB full color display, 3072 signal lines are required for an XGA class and 4800 signal lines are required for a UXGA class. Such a plurality of signal lines are divided into several blocks at the end portion of the pixel portion 3701, thereby forming leading lines, and gathered corresponding to the pitch of output terminals of each driver IC.

The driver IC is preferably formed using a crystalline semiconductor formed over a substrate. The crystalline semiconductor is preferably formed by being irradiated with continuous wave laser light. Therefore, continuous wave solid-state laser or continuous wave gas laser is used for an oscillator for generating the laser light. By using a continuous wave laser, a transistor can be manufactured using a polycrystalline semiconductor layer with few crystal defects and a large grain size. In addition, high-speed driving is possible because mobility and response speed are good, an operating frequency of an element can be improved as compared with a conventional element, and variation in characteristics is small; therefore, high reliability can be obtained. Note that a channel length direction of the transistor and a scanning direction of laser light preferably correspond with each other in order to further improve the operating frequency. This is because the highest mobility can be obtained when a channel length direction of a transistor and a scanning direction of laser light with respect to a substrate are almost parallel to each other (preferably, the angle between them is equal to or larger than −30° and equal to or less than 30°) in a step of laser crystallization with continuous wave laser. Note that the channel length direction corresponds to a direction in which current flows, in other words, a direction in which electric charge moves, in a channel formation region. The transistor thus formed has an active layer including a polycrystalline semiconductor layer in which crystal grains are extended in the channel length direction, and this means that crystal grain boundaries are formed almost along the channel length direction.

In order to perform laser crystallization, it is preferable to significantly narrow laser light, and the shape of the laser light (beam spot) preferably has the width that is the same as a short side of each driver IC, which is equal to or larger than 1 mm and equal to or less than 3 mm. In addition, in order to secure an enough and effective energy density for an object to be irradiated, an irradiated region with laser light preferably has a linear shape. Note that the term “linear” used herein means not a line in a strict sense but a rectangle or an oblong with a large aspect ratio. For example, it refers to a rectangle or an oblong with an aspect ratio of 2 or more (preferably equal to or larger than 10 and equal to or less than 10000). Thus, by making a width of the laser light shape (beam spot) as long as a short side of each driver IC, a method for manufacturing a display device, by which productivity is improved, can be provided.

As shown in FIGS. 26A and 26B, driver ICs may be mounted for both the scan line driver circuit and the signal line driver circuit. In this case, it is preferable to use driver ICs having different specifications for the scan line driver circuit and the signal line driver circuit.

In the pixel portion, signal lines and scan lines intersect to form a matrix, and a transistor is arranged corresponding to each intersection. In the present invention, a TFT including an amorphous semiconductor or a semi-amorphous semiconductor for a channel portion is used as a transistor arranged in the pixel portion. The amorphous semiconductor is formed by a method such as a plasma CVD method or a sputtering method. The semi-amorphous semiconductor can be formed by a plasma CVD method at a temperature of 300° C. or lower; for example, a film thickness required for forming the transistor is formed in a short time even in the case of using, for example, a non-alkaline glass substrate having an external size of 550 mm×650 mm. The feature of such a manufacturing technique is effective in manufacturing a large-screen display device. Further, a semi-amorphous TFT can obtain field effect mobility of 2-10 cm²/V·sec by formation of a channel formation region using an SAS. With the use of the present invention, a pattern can be formed into a desired shape with high controllability; therefore, a minute wiring can be stably formed without generation of a defect such as a short circuit. Thus, a display panel where system-on-panel is realized can be manufactured.

The scan line driver circuit can also be formed over the same substrate as the pixel portion by using a TFT having a semiconductor layer formed of an SAS. When a TFT having a semiconductor layer formed of an AS is used, driver ICs are preferably mounted for both the scan line driver circuit and the signal line driver circuit.

In the latter case, it is preferable to use driver ICs having different specifications for the scan line driver circuit and the signal line driver circuit. For example, a transistor included in the scan line driver IC is required to withstand a voltage of approximately 30 V and since a drive frequency is less than or equal to 100 kHz, high-speed operation is not relatively required. Therefore, it is preferable to set a channel length (L) of the transistor included in the scan line driver sufficiently long. On the other hand, a transistor of the signal line driver IC is required to withstand a voltage of only approximately 12 V and since a drive frequency is approximately 65 MHz at 3 V, high-speed operation is required. Therefore, it is preferable to set a channel length and the like of the transistor included in the driver with a micron rule.

A method for mounting each driver IC is not particularly limited, and a COG method, a wire bonding method, or a TAB method can be employed.

By setting the thicknesses of each driver IC and the counter substrate so as to be equal to each other, there is almost no difference in height between each driver IC and the counter substrate, which contributes to thinning of a display device as a whole. Further, by forming both the substrates of the same material, thermal stress is not generated and characteristics of a circuit including a TFT are not damaged even when a temperature change is caused in the display device. Furthermore, by mounting each driver IC, which has a longer side than an IC chip, for the driver circuit as described in this embodiment mode, the number of driver ICs to be mounted for one pixel portion can be reduced.

As described above, each driver circuit can be incorporated into a display panel.

Embodiment Mode 13

Described below is an example in which a semiconductor layer is formed of an amorphous semiconductor or an SAS and a scan line driver circuit is formed over a substrate in a display panel (an EL display panel or a liquid crystal display panel) manufactured in accordance with each of Embodiment Modes 4 to 11.

FIG. 31 is a block diagram of a scan line driver circuit including an n-channel TFT which uses an SAS with an electron field-effect mobility of 1-15 cm²/V·sec.

In FIG. 31, a block denoted by reference numeral 8500 corresponds to a pulse output circuit for outputting sampling pulses for one stage. A shift register includes n pulse output circuits. Reference numeral 8501 denotes a buffer circuit and a pixel 8502 is connected to the buffer circuit.

FIG. 32 shows a specific structure of the pulse output circuit 8500, which includes n-channel TFTs 8601 to 8613. In this case, the size of each TFT may be determined in consideration of operation characteristics of an n-channel TFT using an SAS. For example, when the channel length is 8 μm, the channel width can be set in the range of 10-80 μm.

Further, a specific structure of the buffer circuit 8501 is shown in FIG. 33. Similarly, the buffer circuit includes n-channel TFTs 8620 to 8635. In this case, the size of each TFT may be determined in consideration of operation characteristics of an n-channel TFT using an SAS. For example, when the channel length is 10 μm, the channel width can be set in the range of 10-1800 μm.

In order to realize such a circuit, the TFTs are required to be connected to one another with a wiring.

As described above, each driver circuit can be incorporated into a display panel.

Embodiment Mode 14

This embodiment mode is described with reference to FIG. 16. FIG. 16 shows an example in which an EL display module is formed using a TFT substrate 2800 which is manufactured using the present invention. In FIG. 16, a pixel portion including pixels is formed over the TFT substrate 2800.

In FIG. 16, outside the pixel portion and between a driver circuit and the pixel portion, a protective circuit portion 2801 which is a similar TFT to the pixel portion or the TFT functioning like a diode by connection between a gate and one of source and drain thereof, is provided. As a driver circuit 2809, a driver IC formed using a single crystalline semiconductor, a stick driver IC formed using a polycrystalline semiconductor film over a glass substrate, a driver circuit formed using an SAS, or the like is applied.

The TFT substrate 2800 is attached firmly to a sealing substrate 2820 with spacers 2806 a and 2806 b formed by a droplet discharging method interposed therebetween. The spacers are preferably provided to keep an interval between the two substrates constant even when the substrates are thin and/or an area of the pixel portion is increased. A space between the TFT substrate 2800 and the sealing substrate 2820 over light-emitting elements 2804 and 2805 connected to TFTs 2802 and 2803 respectively, may be filled with a resin material having a light-transmitting property against at least visible light, and solidified. Alternatively, the space may be filled with anhydrous nitrogen or an inert gas.

FIG. 16 shows the case where the light-emitting elements 2804 and 2805 are top-emission type and light is emitted in each direction denoted by arrows in the drawing. Multicolor display can be performed by making pixels to emit light of different colors of red, green, and blue. At this time, color purity of light emitted to outside can be improved by providing colored layers 2807 a, 2807 b, and 2807 c corresponding to respective colors on the sealing substrate 2820 side. Moreover, pixels formed as white light-emitting elements may be combined with the colored layers 2807 a, 2807 b, and 2807 c.

The driver circuit 2809 which is an external circuit is connected to a scan line or signal line connection terminal which is provided at one end of an external circuit board 2811, by a wiring board 2810. Further, a heat pipe 2813 which is a highly efficient thermal conductive device with a pipe shape and a heat sink 2812, which are used for radiating heat to the outside of the device, may be provided so as to be in contact with or adjacent to the TFT substrate 2800 to increase a heat radiation effect.

Note that FIG. 16 shows the top-emission EL module; however, a bottom-emission structure may be employed by changing the structure of each light-emitting element or the arrangement of the external circuit board. It is needless to say that a dual-emission structure in which light is emitted from both of a top surface and a bottom surface may be used. In the case of a top-emission structure, an insulating layer serving as a partition wall may be colored and used as a black matrix. This partition wall can be formed by a droplet discharging method, and it may be formed by mixing a black resin of a pigment material, carbon black, or the like into a resin material such as polyimide, and a stacked layer thereof may also be used as the partition wall.

Further, in an EL display module, reflected light of light entering from outside may be blocked with the use of a retardation film or a polarizing plate. In a top-emission display device, an insulating layer serving as a partition wall may be colored and used as a black matrix. This partition wall can also be formed by a droplet discharging method, and it may be formed by mixing a black resin of carbon black or the like into a black resin of a pigment material, or a resin material such as polyimide, and a stacked layer thereof may also be used as the partition wall. By a droplet discharging method, different materials may be discharged to the same region plural times to form the partition wall. A quarter wave (λ/4) plate or a half wave (λ/2) plate may be used as each retardation film such that light can be controlled. As a structure, there is a structure in which the light-emitting element, the sealing substrate (sealing member), the retardation films (the quarter wave plate (λ/4) and the half wave plate (λ/2)), and the polarizing plate are sequentially provided over a TFT element substrate, and light emitted from the light-emitting element is transmitted therethrough and is emitted to outside from a polarizing plate side. The retardation film or polarizing plate may be provided on a side from which light is emitted or may be provided on both sides in the case of a dual-emission display device in which light is emitted from both the sides. In addition, an anti-reflective film may be provided on the outer side of the polarizing plate. Accordingly, higher definition and precise images can be displayed.

As for the TFT substrate 2800, a sealing structure may be formed by attaching a resin film using a sealing member or an adhesive resin to the side provide with the pixel portion. Although glass sealing using a glass substrate is described in this embodiment mode, various sealing methods such as resin sealing using a resin, plastic sealing using plastic, and film sealing using a film can be employed. A gas barrier film which prevents water vapor from penetrating the resin film is preferably provided on the resin film. By employing a film sealing structure, further reduction in thickness and weight can be achieved.

This embodiment mode can be combined with any of Embodiment Modes 1 to 8, 12, and 13.

Embodiment Mode 15

This embodiment mode is described with reference to FIGS. 20A and 20B. FIGS. 20A and 20B show examples in which a liquid crystal display module is formed using a TFT substrate 2600 manufactured using the present invention.

FIG. 20A is an example of a liquid crystal display module. The TFT substrate 2600 and a counter substrate 2601 are firmly attached to each other with a sealing member 2602, and a pixel portion 2603 and a liquid crystal layer 2604 are provided therebetween to form a display region. A colored layer 2605 is required in the case of performing color display, and colored layers corresponding to red, green, and blue respectively are provided for pixels in the case of an RGB mode. A polarizing plate 2606 is provided outside the counter substrate 2601, and a polarizing plate 2607 and a diffusing plate 2613 are provided outside the TFT substrate 2600. A light source includes a cold cathode tube 2610 and a reflective plate 2611, and a circuit substrate 2612 is connected to the TFT substrate 2600 by a flexible wiring board 2609 and includes an external circuit such as a control circuit or a power source circuit. Further, a driver circuit 2608 provided for the TFT substrate 2600 is connected to a scan line or signal line connection terminal which is provided at one end of the external circuit board 2612 by the wiring board 2609. In addition, a retardation film may be interposed between the polarizing plate and the liquid crystal layer.

For the liquid crystal display module, the following can be used: a TN (Twisted Nematic) mode, an IPS (In-Plane-Switching) mode, an FFS (Fringe Field Switching) mode, an MVA (Multi-domain Vertical Alignment) mode, a PVA (Patterned Vertical Alignment) mode, an ASM (Axially Symmetric aligned Micro-cell) mode, an OCB (Optical Compensated Birefringence) mode, an FLC (Ferroelectric Liquid Crystal) mode, an AFLC (AntiFerroelectric Liquid Crystal) mode, or the like.

FIG. 20B shows an example of an FS-LCD (Field Sequential-LCD) in which an OCB mode is applied to the liquid crystal display module of FIG. 20A. The FS-LCD emits light of red, green, and blue during one frame period and can perform color display by combining images with time division. Since light of each color is emitted by a light-emitting diode, a cold cathode tube, or the like, a color filter is not necessary. Thus, it is not necessary to arrange color filters of three primary colors and restrict the display region of each color, and display of all three colors can be performed in any region. On the other hand, since light of three colors is emitted during one frame period, high-speed response of liquid crystals is necessary. An FLC mode, an OCB mode, or the like using an FS method is employed for a display device of the present invention, so that high performance and high image quality display device and liquid crystal television set can be completed.

A liquid crystal layer of an OCB mode has a so-called π-cell structure. In the π-cell structure, liquid crystal molecules are aligned so that their pretilt angles are plane-symmetric along a center plane between an active matrix substrate and a counter substrate. An orientation state in the π-cell structure is splay orientation when voltage is not applied between the substrates, and then shifts to bend orientation when voltage is applied therebetween. With this bend orientation state, white display is obtained. When voltage is further applied, liquid crystal molecules of bend-orientation get orientated so as to be perpendicular to both the substrates so that light is not transmitted. Note that by employing the OCB mode, response which is about 10 times as rapid as that of a conventional TN mode can be achieved.

Moreover, as a mode for the FS method, an HV (Half-V)-FLC, an SS (Surface Stabilized)-FLC, or the like using a ferroelectric liquid crystal (FLC) capable of high-speed operation may be used. The OCB mode can use a nematic liquid crystal having relatively low viscosity, and the HV-FLC or the SS-FLC can use a smectic liquid crystal having a ferroelectric phase.

Moreover, optical response speed of a liquid crystal display module is increased by narrowing the cell gap of the liquid crystal display module. In addition, the optical response speed can also be increased by decreasing the viscosity of the liquid crystal material. The increase in response speed is particularly effective when a pixel pitch in a pixel region of a TN mode liquid crystal display module is 30 μm or less. Further, further increase in response speed is possible by an overdrive method in which an applied voltage is increased (or decreased) only for just a moment.

FIG. 20B shows a transmissive liquid crystal display module, in which a red light source 2910 a, a green light source 2910 b, and a blue light source 2910 c are provided as light sources. A control portion 2912 is provided in order to switch on or off of the red light source 2910 a, the green light source 2910 b, and the blue light source 2910 c. The control portion 2912 controls light emission of each color, so that light enters liquid crystals, and images are combined using time division, thereby color display is performed.

Thus, by using the present invention, a high-definition and highly reliable liquid crystal display module can be manufactured.

This embodiment mode can be combined with any of Embodiment Modes 1 to 3, and 9 to 13.

Embodiment Mode 16

A television set (also called just a TV or a television receiver) can be completed using the display device formed by the present invention. FIG. 27 is a block diagram showing a main structure of a television set.

FIG. 25A is a top diagram showing a structure of a display panel of the present invention, in which the pixel portion 2701 in which the pixels 2702 are arranged in matrix, the scan line input terminal 2703, and the signal line input terminal 2704 are formed over the substrate 2700 having an insulating surface. The number of pixels may be set in accordance with various standards: the number of pixels of XGA for RGB full-color display may be 1024×768×3 (RGB), that of UXGA for RGB full-color display may be 1600×1200×3 (RGB), and that corresponding to a full-spec high vision for RGB full-color display may be 1920×1080×3 (RGB).

Scan lines extended from the scan line input terminal 2703 intersect with signal lines extended from the signal line input terminal 2704, and the pixels 2702 are arranged in matrix at intersections thereof. Each pixel 2702 in the pixel portion 2701 is provided with a switching element and a pixel electrode layer connected to the switching element. A typical example of the switching element is a TFT. The gate electrode layer side of the TFT is connected to the scan line, and the source or drain side thereof is connected to the signal line, so that each pixel can be controlled independently by signals inputted from outside.

FIG. 25A shows a structure of the display panel in which signals inputted to the scan lines and signal lines are controlled by an external driver circuit. Alternatively, the driver ICs 2751 may be mounted on the substrate 2700 by a COG (Chip On Glass) method as shown in FIG. 26A. As another mounting mode, a TAB (Tape Automated Bonding) method may be employed as shown in FIG. 26B. Each driver IC may be formed using a single crystalline semiconductor substrate or may be formed using a TFT over a glass substrate. In FIGS. 26A and 26B, each driver IC 2751 is connected to the FPC (Flexible Printed Circuit) 2750.

Further, in the case where the TFT provided in each pixel is formed using a semiconductor having crystallinity, the scan line driver circuit 3702 can also be formed over the substrate 3700 as shown in FIG. 25B. In FIG. 25B, the pixel portion 3701 is controlled by an external driver circuit, similarly to that, which is connected to the signal line input terminal 3704, in FIG. 25A. In the case where the TFT provided in each pixel is formed using a polycrystalline (microcrystalline) semiconductor, a single crystalline semiconductor, or the like with high mobility, the pixel portion 4701, the scan line driver circuit 4702, and the signal line driver circuit 4704 can be formed over the substrate 4700 as shown in FIG. 25C.

In FIG. 27, a display panel can be formed to have any mode of the following: the structure as shown in FIG. 25A, in which only a pixel portion 901 is formed over a substrate, and a scan line driver circuit 903 and a signal line driver circuit 902 are mounted by a TAB method as shown in FIG. 26B or by a COG method as shown in FIG. 26A; the structure as shown in FIG. 25B, in which a TFT is formed, the pixel portion 901 and the scan line driver circuit 903 are formed over the substrate, and the signal line driver circuit 902 is separately mounted as a driver IC; the structure as shown in FIG. 25C, in which the pixel portion 901, the signal line driver circuit 902, and the scan line driver circuit 903 are formed over the substrate; and the like.

In FIG. 27, as a further structure of the external circuit, a video signal amplifier circuit 905 for amplifying a video signal among signals received by a tuner 904, a video signal processing circuit 906 for converting signals outputted from the video signal amplifier circuit 905 into chrominance signals corresponding to colors of red, green, and blue respectively, a control circuit 907 for converting the video signal so as to be inputted to each driver IC, and the like are provided on the video signal input side. The control circuit 907 outputs signals to both the scan line side and the signal line side. In the case of digital driving, a signal dividing circuit 908 may be provided on the signal line side and an input digital signal may be divided into m signals and supplied.

Among signals received by the tuner 904, an audio signal is transmitted to an audio signal amplifier circuit 909, and an output of the audio signal amplifier circuit 909 is supplied to a speaker 913 through an audio signal processing circuit 910. A control circuit 911 receives control information on a receiving station (receiving frequency) or sound volume from an input portion 912 and transmits signals to the tuner 904 and the audio signal processing circuit 910.

A television set can be completed by incorporating the display module into a chassis as shown in FIGS. 28A and 28B. When a liquid crystal display module is used as the display module, a liquid crystal television set can be manufactured. When an EL display module is used, an EL television set can be manufactured. Further, a plasma television, electronic paper, or the like can be manufactured. In FIG. 28A, a main screen 2003 is formed using the display module, and a speaker portion 2009, an operation switch, and the like are provided as its accessory equipment. Thus, a television set can be completed by the present invention.

A display panel 2002 is incorporated in a chassis 2001. With the use of a receiver 2005, in addition to reception of general TV broadcast, communication of information can also be performed either in one way (from a transmitter to a receiver) or in two ways (between a transmitter and a receiver or between receivers) by connection to a wired or wireless communication network through a modem 2004. The television set can be operated by switches incorporated in the chassis or by a remote control device 2006 separated from the main body. A display portion 2007 that displays information to be outputted may also be provided for this remote control device.

Further, in the television set, a structure for displaying a channel, sound volume, or the like may be additionally provided by providing a subscreen 2008 using a second display panel in addition to the main screen 2003. In this structure, the main screen 2003 and the subscreen 2008 can be formed using the liquid crystal display panel of the present invention, or the main screen 2003 may be formed using an EL display panel superior in viewing angle whereas the subscreen 2008 may be formed using a liquid crystal display panel capable of displaying with low power consumption. Further, in order to prioritize low power consumption, a structure in which the main screen 2003 is formed using a liquid crystal display panel, the subscreen 2008 is formed using an EL display panel, and the sub-screen is able to flash on and off may be employed. By the present invention, a highly reliable display device can be manufactured even when such a large substrate and many TFTs and electronic components are used.

FIG. 28B shows a television set having a large display portion, e.g., a 20-inch to 80-inch display portion, which includes a chassis 2010, a display portion 2011, a remote control device 2012 which is an operation portion, a speaker portion 2013, and the like. The present invention is applied to manufacture the display portion 2011. The television set shown in FIG. 28B is a wall-hanging type, and does not need a wide space.

It is necessary to say that the present invention is not limited to the television set and is also applicable to various uses as a display medium having a large area, such as a monitor of a personal computer, an information display board at a train station, an airport, or the like, or an advertisement display board on the street.

This embodiment mode can be freely combined with any of Embodiment Modes 1 to 15 as appropriate.

Embodiment Mode 17

Electronic devices of the present invention include a television set (also simply called a TV or a television receiver), a camera such as a digital camera or a digital video camera, a mobile phone set (also simply called a mobile phone), a portable information terminal such as a PDA, a portable game machine, a monitor for a computer, a computer, an audio reproducing device such as a car audio set, an image reproducing device provided with a recording medium, such as a home-use game machine, and the like. Specific examples thereof are described with reference to FIGS. 29A to 29E.

A portable information terminal shown in FIG. 29A includes a main body 9201, a display portion 9202, and the like. The display device of the present invention can be applied to the display portion 9202. Accordingly, since manufacturing through a simplified process at low cost is possible, a highly reliable portable information terminal can be provided at low cost.

A digital video camera shown in FIG. 29B includes a display portion 9701, a display portion 9702, and the like. The display device of the present invention can be applied to the display portion 9701. Accordingly, since manufacturing through a simplified process at low cost is possible, a highly reliable digital video camera can be provided at low cost.

A mobile phone shown in FIG. 29C includes a main body 9101, a display portion 9102, and the like. The display device of the present invention can be applied to the display portion 9102. Accordingly, since manufacturing through a simplified process at low cost is possible, a highly reliable mobile phone can be provided at low cost.

A portable television set shown in FIG. 29D includes a main body 9301, a display portion 9302, and the like. The display device of the present invention can be applied to the display portion 9302. Accordingly, since manufacturing through a simplified process at low cost is possible, a highly reliable television set can be provided at low cost. Further, the display device of the present invention can be applied to various types of television sets including a small-sized one mounted on a portable terminal such as a mobile phone, a medium-sized one that is portable, and a large-sized (e.g., 40-inch or larger) one.

A portable computer shown in FIG. 29E includes a main body 9401, a display portion 9402, and the like. The display device of the present invention can be applied to the display portion 9402. Accordingly, since manufacturing through a simplified process at low cost is possible, a highly reliable computer can be provided at low cost.

As described above, by using the display device of the present invention, a highly-reliable, high-performance electronic device can be provided at a low price.

This embodiment mode can be freely combined with any of Embodiment Modes 1 to 16 as appropriate.

This application is based on Japanese Patent Application serial no. 2006-228350 filed in Japan Patent Office on 24th, Aug., 2006, the entire contents of which are hereby incorporated by reference. 

1. A method for manufacturing a display device, comprising the steps of: forming a light-absorbing layer selectively over an insulating surface; forming an insulating layer over the insulating surface and the light-absorbing layer; irradiating the insulating surface, the light-absorbing layer, and the insulating layer with laser light to selectively remove the insulating layer above the light-absorbing layer so that an opening reaching the light-absorbing layer is formed in the insulating layer; and forming a conductive film in the opening so as to be in contact with the light-absorbing layer.
 2. A method for manufacturing a display device, comprising the steps of: forming a conductive layer selectively over an insulating surface; forming a light-absorbing layer over the conductive layer; forming an insulating layer over the insulating surface and the light-absorbing layer; irradiating the insulating surface, the light-absorbing layer, and the insulating layer with laser light to selectively remove the insulating layer above the light-absorbing layer so that an opening reaching the light-absorbing layer is formed in the insulating layer; and forming a conductive film in the opening so as to be in contact with the light-absorbing layer.
 3. A method for manufacturing a display device, comprising the steps of: forming a conductive layer selectively over an insulating surface; forming a light-absorbing layer over the conductive layer; forming an insulating layer over the insulating surface and the light-absorbing layer; irradiating the insulating surface, the light-absorbing layer, and the insulating layer with laser light to selectively remove the light-absorbing layer in an irradiated region with the laser light and the insulating layer above the light-absorbing layer so that an opening reaching the light-absorbing layer and the conductive layer is formed in the insulating layer; and forming a conductive film in the opening so as to be in contact with the light-absorbing layer and the conductive layer.
 4. A method for manufacturing a display device, comprising the steps of: forming a plurality of light-absorbing layers over an insulating surface; forming an insulating layer over the insulating surface and the plurality of light-absorbing layers; irradiating the insulating surface, the plurality of light-absorbing layers, and the insulating layer with laser light to selectively remove the insulating layer above the plurality of light-absorbing layers so that a plurality of openings is formed in the insulating layer; and forming a conductive film in the plurality of openings so as to be in contact with the plurality of light-absorbing layers.
 5. The method for manufacturing the display device according to any one of claims 1 to 4, wherein the light-absorbing layer is formed of a conductive material.
 6. The method for manufacturing the display device according to claim 5, wherein the light-absorbing layer comprises a material selected from the group consisting of chromium, tantalum, silver, molybdenum, nickel, titanium, cobalt, copper, aluminum, and a combination thereof
 7. The method for manufacturing the display device according to any one of claims 1 to 4, wherein the light-absorbing layer is formed of a semiconductor material.
 8. The method for manufacturing the display device according to claim 7, wherein the light-absorbing layer is formed of silicon.
 9. The method for manufacturing the display device according to any one of claims 1 to 4, wherein the opening is formed by the laser light with a wavelength which is transmitted through the insulating layer. 